ALBERT

Description: We present measurements of higher order clustering of galaxies in the latest release of the Canada–France–Hawaii Telescope Legacy Survey (CFHTLS)-Wide. We construct a series of volume-limited sample of galaxies containing more than one million galaxies over the redshift range 0.2 〈  z  〈 1 in the four independent fields of the CFHTLS-Wide. Using a counts-in-cells technique we measure the variance ${\bar{\xi }}_2$ and the hierarchical moments $S_{n}= {{\bar{\xi }}_n / {\bar{\xi }}_2^{n-1}}$ (3 ≤  n  ≤ 5) as a function of redshift and angular scale. We find that the measured field-to-field scatter in our estimators is in excellent agreement with analytical predictions. At small scales, corresponding to the highly non-linear regime, we find tentative evidence at the 1 level that the hierarchical moments increase with redshift. At large scales, corresponding to the weakly non-linear regime, our measurements are marginally consistent with perturbation theory predictions for standard cold dark matter cosmology using a simple linear bias. The predictions of perturbation theory tend to slightly overestimate our measurements, which may be a signature of non-linear bias.

Description: We estimate cosmic microwave background (CMB) polarization power spectra and temperature–polarization cross-spectra, from the 9-year data of the Wilkinson Microwave Anisotropy Probe ( WMAP ). Foreground cleaning is implemented using minimum variance linear combinations of the coefficients of needlet decompositions of sky maps for all WMAP channels, to produce maps for CMB temperature anisotropies ( T -mode) and polarization ( E and B -modes), for nine different years of observation. The final power spectra are computed from averages of all possible cross-year power spectra obtained using foreground-cleaned maps for the different years. Our analysis technique yields a measurement of the EE spectrum that is in excellent agreement with theoretical expectations from the current cosmological model. By comparison, the publicly available WMAP EE power spectrum is higher on average (and significantly higher than the predicted EE spectrum from the current best fit) at scales larger than about a degree, an excess that is not confirmed by our analysis. Our TE and TB measurements are in good agreement overall with the WMAP ones and are compatible with the theoretical expectations, although a few data points are off by a few standard deviations, and yield a reduced 2 somewhat above expectation. As predicted for a standard cosmological model with low tensor-to-scalar ratio, the EB and BB power spectra obtained in our analysis are compatible with zero.

Description: We present optical integral field unit observations of two gas pillars surrounding the Galactic young massive star cluster NGC 3603. The high S/N and spectral resolution of these data have allowed us to accurately quantify the Hα, [N ii ] and [S ii ] emission line shapes, and we find a mixture of broad (FWHM ~ 70–100 km s –1 ) and narrow (〈50 km s –1 ) components. The broad components are found close to the edges of both pillars, suggesting that they originate in turbulent mixing layers (TMLs) driven by the effect of the star cluster wind. Both pillars exhibit surprisingly high ionized gas densities of 〉10 000 cm –3 . In one pillar we found that these high densities are only found in the narrow component, implying that they must originate from deeper within the pillar than the broad component. From this, together with our kinematical data, we conclude that the narrow component traces a photoevaporation flow, and that the TML forms at the interface with the hot wind. On the pillar surfaces, we find a consistent offset in radial velocity between the narrow (brighter) components of Hα and [N ii ] of ~5–8 km s –1 , for which we were unable to find a satisfactory explanation. We urge the theoretical community to simulate mechanical and radiative cloud interactions in more detail to address the many unanswered questions raised by this study.

Description: By exploiting the data base of early-type galaxy (ETG) members of the WINGS survey of nearby clusters, we address here the long debated question of the origin and shape of the Fundamental Plane (FP). Our data suggest that different physical mechanisms concur in shaping and ‘tilting’ the FP with respect to the virial plane (VP) expectation. In particular, a ‘hybrid solution’ in which the structure of galaxies and their stellar population are the main contributors to the FP tilt seems to be favoured. We find that the bulk of the tilt should be attributed to structural non-homology, while stellar population effects play an important but less crucial role. In addition, our data indicate that the differential FP tilt between the V and K band is due to a sort of entanglement between structural and stellar population effects, for which the inward steepening of colour profiles ( V  –  K ) tends to increase at increasing the stellar mass of ETGs. The same kind of analysis applied to the ATLAS 3 D and Sloan Digital Sky Survey (SDSS) data in common with WINGS ( WSDSS throughout the paper) confirms our results, the only remarkable difference being the less important role that our data attribute to the stellar mass-to-light-ratio (stellar populations) in determining the FP tilt . The ATLAS 3 D data also suggest that the FP tilt depends as well on the dark matter (DM) fraction and on the rotational contribution to the kinetic energy ( V rot /), thus again pointing towards the above-mentioned ‘hybrid solution’. We show that the global properties of the FP, i.e. its tilt and tightness, can be understood in terms of the underlying correlation among mass, structure and stellar population of ETGs, for which, at increasing the stellar mass, ETGs become (on average) ‘older’ and more centrally concentrated. Finally, we show that a Malmquist-like selection effect may mimic a differential evolution of the mass-to-light ratio for galaxies of different masses. This should be taken into account in the studies investigating the amount of the so-called ‘downsizing’ phenomenon.

Description: I present a new algorithm, Curved-sky grAvitational Lensing for Cosmological Light conE simulatioNS ( calclens ), for efficiently computing weak gravitational lensing shear signals from large N -body light cone simulations over a curved sky. This new algorithm properly accounts for the sky curvature and boundary conditions, is able to produce redshift-dependent shear signals including corrections to the Born approximation by using multiple-plane ray tracing and properly computes the lensed images of source galaxies in the light cone. The key feature of this algorithm is a new, computationally efficient Poisson solver for the sphere that combines spherical harmonic transform and multigrid methods. As a result, large areas of sky (~10 000 square degrees) can be ray traced efficiently at high resolution using only a few hundred cores. Using this new algorithm and curved-sky calculations that only use a slower but more accurate spherical harmonic transform Poisson solver, I study the convergence, shear E-mode, shear B-mode and rotation mode power spectra. Employing full-sky E/B-mode decompositions, I confirm that the numerically computed shear B-mode and rotation mode power spectra are equal at high accuracy (1 per cent) as expected from perturbation theory up to second order. Coupled with realistic galaxy populations placed in large N -body light cone simulations, this new algorithm is ideally suited for the construction of synthetic weak lensing shear catalogues to be used to test for systematic effects in data analysis procedures for upcoming large-area sky surveys. The implementation presented in this work, written in c and employing widely available software libraries to maintain portability, is publicly available at http://code.google.com/p/calclens .

Description: Quasar accretion disc winds observed via broad absorption lines (BALs) in the UV produce strong continuous absorption in X-rays. The X-ray absorber is believed to serve critically as a radiative shield to keep the outflow ionizations low enough for radiative driving. However, previous studies have shown that ‘mini-BAL’ and narrow absorption line (NAL) outflows have dramatically less X-ray absorption than BALs. Here, we examine X-ray and rest-frame UV spectra of eight mini-BAL quasars with outflow speeds in the range 0.1–0.2c to test the hypothesis that these extreme speeds require a strong shield. We find that the X-ray absorption is weak or moderate, with neutral-equivalent column densities N H  〈 few 10 22 cm –2 , consistent with mini-BALs at lower speeds. We use photoionization models to show that the amount of shielding consistent with our data is too weak to control the outflow ionizations and, therefore, it is not important for the acceleration. Shielding in complex geometries also seems unlikely because the alleged shield would need to extinguish the ionizing far-UV flux while avoiding detection in X-rays and the near-UV. We argue that the outflow ionizations are kept moderate, instead, by high gas densities in small clouds. If the mini-BALs form at radial distances of the order of R ~ 2 pc from the central quasar (broadly consistent with theoretical models and with the mini-BAL variabilities observed here and in previous work), and the total column densities in the mini-BAL gas are N H 10 21 cm –2 , then the total radial extent of outflow clouds is only R clouds 3 x 10 13 cm in cases of no/weak shielding or R clouds 3 x 10 14 cm behind the maximum shield allowed by our data. This implies radial filling factors R clouds / R 5 x 10 – 6 or 5 x 10 – 5 for the unshielded or maximally shielded cases, respectively. Compared to the transverse sizes 8 x 10 15 cm (based on measured line depths), the outflows have shapes like thin ‘pancakes’ viewed face-on, or they occupy larger volumes like a spray of many dense clouds with a small volume filling factor. These results favour models with magnetic confinement in magnetic disc winds. To the extent that BALs, mini-BALs and NALs probe the same general outflow phenomenon, our result for dense substructures should apply to all three outflow types.

Description: The estimated stellar masses of galaxies are widely used to characterize how the galaxy population evolves over cosmic time. If stellar masses can be estimated in a robust manner, free from any bias, global diagnostics such as the stellar mass function can be used to constrain the physics of galaxy formation. We explore how galaxy stellar masses, estimated by fitting broad-band spectral energy distributions (SEDs) with stellar population models, can be biased as a result of commonly adopted assumptions for the star formation and chemical enrichment histories, recycled fractions and dust attenuation curves of galaxies. We apply the observational technique of broad-band SED fitting to model galaxy SEDs calculated by the theoretical galaxy formation model GALFORM, isolating the effect of each of these assumptions. We find that, averaged over the entire galaxy population, the common assumption of exponentially declining star formation histories does not, by itself, adversely affect stellar mass estimation. However, we also show that this result does not hold when considering galaxies that have undergone a recent burst of star formation. We show that fixing the metallicity in SED fitting or using sparsely sampled metallicity grids can introduce mass-dependent systematics into stellar mass estimates. We find that the common assumption of a star–dust geometry corresponding to a uniform foreground dust screen can cause the stellar masses of dusty model galaxies to be significantly underestimated. Finally, we show that stellar mass functions recovered by applying SED fitting to model galaxies at high redshift can differ significantly in both shape and normalization from the intrinsic mass functions predicted by a given model. In particular, the effects of dust can reduce the normalization at the high-mass end by up to 0.6 dex in some cases. Given these differences, our methodology of using stellar masses estimated from model galaxy SEDs offers a new, self-consistent way to compare model predictions with observations. We conclude that great care should be taken when comparing theoretical galaxy formation models to observational results based on the estimated stellar masses of high-redshift galaxies.

Description: We analyse the 2D correlation function of the Sloan Digital Sky Survey-III Baryon Oscillation Spectroscopic Survey (BOSS) CMASS sample of massive galaxies of the ninth data release to measure cosmic expansion H and the angular diameter distance D A at a mean redshift of 〈 z 〉 = 0.57. We apply, for the first time, a new correlation function technique called clustering wedges μ ( s ). Using a physically motivated model, the anisotropic baryonic acoustic feature in the galaxy sample is detected at a significance level of 4.7 compared to a featureless model. The baryonic acoustic feature is used to obtain model-independent constraints cz / H / r s = 12.28 ± 0.82 (6.7 percent accuracy) and D A / r s =  9.05 ± 0.27 (3.0 per cent) with a correlation coefficient of –0.5, where r s is the sound horizon scale at the end of the baryonic drag era. We conduct thorough tests on the data and 600 simulated realizations, finding robustness of the results regardless of the details of the analysis method. Combining this with r s constraints from the cosmic microwave background, we obtain H (0.57) = 90.8 ± 6.2 km s –1 Mpc –1 and D A (0.57) = 1386 ± 45 Mpc. We use simulations to forecast results of the final BOSS CMASS data set. We apply the reconstruction technique on the simulations demonstrating that the sharpening of the anisotropic baryonic acoustic feature should improve the detection as well as tighten constraints of H and D A by ~30 per cent on average.

Description: We present an analysis of Chandra archival, pre-explosion data of the positions of three nearby (〈25 Mpc) Type Ia supernovae, SN2011iv, SN2012cu and SN2012fr. No sources corresponding to the progenitors were found in any of the observations. Combining all sources with well-defined backgrounds does not reveal any evidence for X-ray emission from the progenitors either. We calculated upper limits on the bolometric luminosities of the progenitors, under the assumption that they were black bodies with effective temperatures between 30 and 150 eV, corresponding to ‘canonical’ supersoft X-ray sources. The upper limits of SN2012fr straddle the Eddington luminosity of canonical supersoft sources, but fainter canonical supersoft sources cannot be ruled out by this study. We also compare our upper limits with known compact binary supersoft X-ray sources. This study is a continuation of the campaign to directly detect or constrain the X-ray characteristics of pre-explosion observations of nearby Type Ia supernova progenitors; with the results reported in Nielsen, Voss & Nelemans (see reference in Introduction), the number of nearby Type Ia supernovae for which pre-explosion images are available in the Chandra archive is now 13 and counting.

Description: In this work, we report the Photodetector Array Camera and Spectrometer (PACS) 100 μm/160 μm detections of a sample of 42 GALEX -selected and far-infrared (FIR)-detected Lyman break galaxies (LBGs) at z  ~ 1 located in the Cosmic Evolution Survey (COSMOS) field and analyse their ultraviolet (UV) to FIR properties. The detection of these LBGs in the FIR indicates that they have a dust content high enough so that its emission can be directly detected. According to a spectral energy distribution (SED) fitting with stellar population templates to their UV-to-near-IR observed photometry, PACS-detected LBGs tend to be bigger ( R eff  ~ 4.1 kpc), more massive [log ( M * /M ) ~ 10.7], dustier [ E s ( B  –  V ) ~ 0.40], redder in the UV continuum (β ~ –0.60) and UV-brighter [log ( L UV /L ) ~ 10.1] than PACS-undetected LBGs. PACS-detected LBGs at z  ~ 1 are mostly disc-like galaxies and are located over the green valley and red sequence of the colour–magnitude diagram of galaxies at their redshift. By using their UV and IR emission, we find that PACS-detected LBGs tend to be less dusty and have slightly higher total star formation rates (SFRs) than other PACS-detected UV-selected galaxies within the same redshift range. As a consequence of the selection effect due to the depth of the FIR observations employed, all our PACS-detected LBGs have total IR luminosities, L IR , higher than 10 11 L and thus are luminous IR galaxies. However, none of the PACS-detected LBGs are in the ultra-luminous IR galaxy (ULIRG) regime, L IR  ≥ 10 12 L , where the FIR observations are complete. The finding of ULIRGs-LBGs at higher redshifts ( z  ~ 3) suggests an evolution of the FIR emission of LBGs with cosmic time. In an IRX–β diagram, PACS-detected LBGs at z  ~ 1 tend to be located around the relation for local starburst similarly to other UV-selected PACS-detected galaxies at the same redshift. Consequently, the dust-correction factors obtained with their UV continuum slope allow us to determine their total SFR, unlike at higher redshifts. However, the dust attenuation derived from UV to NIR SED fitting overestimates the total SFR for most of our PACS-detected LBGs in an age-dependent way: the overestimation factor is higher in younger galaxies. This is likely due to the typical degeneracy between dust attenuation and age in the SED fitting with synthetic templates and highlights the importance of the FIR measurements in the analysis of star-forming galaxies at intermediate redshifts.

Description: We study 23 previously published Kepler targets to perform a consistent grid-based Bayesian asteroseismic analysis and compare our results to those obtained via the Asteroseismic Modelling Portal. We find differences in the derived stellar parameters of many targets and their uncertainties. While some of these differences can be attributed to systematic effects between stellar evolutionary models, we show that the different methodologies deliver incompatible uncertainties for some parameters. Using non-adiabatic models and our capability to measure surface effects, we also investigate the dependency of these surface effects on the stellar parameters. Our results suggest a dependence of the magnitude of the surface effect on the mixing length parameter which also, but only minimally, affects the determination of stellar parameters. While some stars in our sample show no surface effect at all, the most significant surface effects are found for stars that are close to the Sun's position in the Hertzsprung–Russell diagram.

Description: We present evidence for a strong relationship between galaxy size and environment for the quiescent population in the redshift range 1 〈  z  〈 2. Environments were measured using projected galaxy overdensities on a scale of 400 kpc, as determined from ~96 000 K -band-selected galaxies from the UKIDSS Ultra Deep Survey (UDS). Sizes were determined from ground-based K -band imaging, calibrated using space-based CANDELS HST observations in the centre of the UDS field, with photometric redshifts and stellar masses derived from 11-band photometric fitting. From the resulting size–mass relation, we confirm that quiescent galaxies at a given stellar mass were typically ~50 per cent smaller at z  ~ 1.4 compared to the present day. At a given epoch, however, we find that passive galaxies in denser environments are on average significantly larger at a given stellar mass. The most massive quiescent galaxies ( M *  〉 2 10 11  M ) at z  〉 1 are typically 50 per cent larger in the highest density environments compared to those in the lowest density environments. Using Monte Carlo simulations, we reject the null hypothesis that the size–mass relation is independent of environment at a significance 〉4.8 for the redshift range 1 〈  z  〈 2. In contrast, the evidence for a relationship between size and environment is much weaker for star-forming galaxies.

Description: We present the results from the Very Large Array radio continuum total power and polarized intensity observations of Stephan's Quintet at 1.43 and 4.86 GHz, along with complementary 4.85- and 8.35-GHz Effelsberg observations. Our study shows a large envelope of radio emission encompassing all the member galaxies and hence a large volume of intergalactic matter. Infall of the galaxy NGC 7318B produces a ridge of intergalactic, polarized emission, for which the magnetic field strength has been estimated as 11.0 ± 2.2 μG, with an ordered component of 2.6 ± 0.8 μG. The energy density of the field within the ridge area is of the same order as estimates of the thermal component, implying that the magnetic field has a significant role in the dynamics of the intergalactic matter. We also report that the tidal dwarf galaxy candidate SQ-B possesses a strong and highly anisotropic magnetic field, with a total strength equal to 6.5 ± 1.9 μG and an ordered component reaching 3.5 ± 1.2 μG, which is comparable to that found in normal-sized galaxies.

Description: We present a simple and efficient phenomenological model for the two-dimensional two-point galaxy correlation function that works well over a wide range of scales, from large scales down to scales as small as 25 h –1 Mpc. Our model incorporates non-linear effects and a scale-dependent galaxy bias on small scales, and it allows the redshift-space distortions to be scale and direction dependent. We validate our model using LasDamas mock catalogues and apply it to the Sloan Digital Sky Survey (SDSS) Data Release Seven (DR7) luminous red galaxies (LRGs). Using only the monopole and quadrupole of the correlation function measured from the SDSS DR7 LRGs, we obtain improved measurements H ( z ) r s ( z d )/ c  = 0.0433 ± 0.0042, D A ( z )/ r s ( z d ) = 6.59 ± 0.46 and f ( z ) 8 ( z ) = 0.429 ± 0.089 at z  = 0.35, using the scale range 25 〈  s  〈 120 h –1 Mpc. We expect our results and model to be useful in tightening dark energy and gravity constraints from the full analysis of current and future galaxy clustering data.

Description: We study the formation and evolution of filamentary configurations of dark matter haloes in voids. Our investigation uses the high-resolution cold dark matter simulation CosmoGrid to look for void systems resembling the VGS_31 elongated system of three interacting galaxies that was recently discovered by the Void Galaxy Survey inside a large void in the Sloan Digital Sky Survey galaxy redshift survey. H  i data revealed these galaxies to be embedded in a common elongated envelope, possibly embedded in intravoid filament. In the CosmoGrid simulation we look for systems similar to VGS_31 in mass, size and environment. We find a total of eight such systems. For these systems, we study the distribution of neighbour haloes, the assembly and evolution of the main haloes and the dynamical evolution of the haloes, as well as the evolution of the large-scale structure in which the systems are embedded. The spatial distribution of the haloes follows that of the dark matter environment. We find that VGS_31-like systems have a large variation in formation time, having formed between 10 Gyr ago and the present epoch. However, the environments in which the systems are embedded evolved to resemble each other substantially. Each of the VGS_31-like systems is embedded in an intravoid wall, that no later than z  = 0.5 became the only prominent feature in its environment. While part of the void walls retain a rather featureless character, we find that around half of them are marked by a pronounced and rapidly evolving substructure. Five haloes find themselves in a tenuous filament of a few h –1 Mpc long inside the intravoid wall. Finally, we compare the results to observed data from VGS_31. Our study implies that the VGS_31 galaxies formed in the same (proto)filament, and did not meet just recently. The diversity amongst the simulated halo systems indicates that VGS_31 may not be typical for groups of galaxies in voids.

Description: Using 3D numerical hydrodynamical simulations, we show that jets launched prior to Type Ia supernova (SN Ia) explosion in the core-degenerate (CD) scenario can account for the appearance of two opposite lobes (‘Ears’) along the symmetry axis of the SN remnant (SNR). In the double-degenerate (DD) and CD scenarios the merger of the two degenerate compact objects is very likely to lead to the formation of an accretion disc, that might launch two opposite jets. In the CD scenario, these jets interact with the envelope ejected during the preceding common envelope phase. If explosion occurs shortly after the merger process, the exploding gas and the jets will collide with the ejected nebula, leading to SNR with axisymmetric components including ‘Ears’. We also explore the possibility that the jets are launched by the companion white dwarf prior to its merger with the core. This last process is similar to the one where jets are launched in some pre-planetary nebulae. The SNR ‘Ears’ in this case are formed by a spherical SN Ia explosion inside an elliptical planetary nebula-like object. We compare our numerical results with two SNRs – Kepler and G299.2–2.9.

Description: Low-mass star-forming regions are more complex than the simple spherically symmetric approximation that is often assumed. We apply a more realistic infall/outflow physical model to molecular/continuum observations of three late Class 0 protostellar sources with the aims of (a) proving the applicability of a single physical model for all three sources and (b) deriving physical parameters for the molecular gas component in each of the sources. We have observed several molecular species in multiple rotational transitions. The observed line profiles were modelled in the context of a dynamical model which incorporates infall and bipolar outflows, using a three-dimensional radiative transfer code. This results in constraints on the physical parameters and chemical abundances in each source. Self-consistent fits to each source are obtained. We constrain the characteristics of the molecular gas in the envelopes as well as in the molecular outflows. We find that the molecular gas abundances in the infalling envelope are reduced, presumably due to freeze-out, whilst the abundances in the molecular outflows are enhanced, presumably due to dynamical activity. Despite the fact that the line profiles show significant source-to-source variation, which primarily derives from variations in the outflow viewing angle, the physical parameters of the gas are found to be similar in each core.

Description: We present predictions for hydrogen and helium emission line luminosities from circumstellar matter around Type Ia supernovae (SNe Ia) using time dependent photoionization modelling. Early high-resolution ESO/Very Large Telescope (VLT) optical echelle spectra of the SN Ia 2000cx were taken before and up to ~70 d after maximum to probe the existence of such narrow emission lines from the supernova. We detect no such lines, and from our modelling place an upper limit on the mass-loss rate for the putative wind from the progenitor system, $\skew4\dot{M}\lesssim 1.3\times 10^{-5} \,{\rm M}_{\odot }\,{\rm yr}^{-1}$ , assuming a speed of 10 km s –1 and solar abundances for the wind. If the wind would be helium-enriched and/or faster, the upper limit on $\skew4\dot{M}$ could be significantly higher. In the helium-enriched case, we show that the best line to constrain the mass-loss would be He i 10 830. In addition to confirming the details of interstellar Na i and Ca ii absorption towards SN 2000cx as discussed by Patat et al., we also find evidence for 6613.56 Å diffuse interstellar band absorption in the Milky Way. We also discuss measurements of the X-ray emission from the interaction between the supernova ejecta and the wind and we re-evaluate observations of SN 1992A obtained ~16 d after maximum by Schlegel & Petre. We find an upper limit of $\skew4\dot{M}\sim 1.3\times 10^{-5} \,{\rm M}_{\odot }\,{\rm yr}^{-1}$ which is significantly higher than that estimated by Schlegel & Petre. These results, together with the previous observational work on the normal SNe Ia 1994D and 2001el, disfavour a symbiotic star in the upper mass-loss rate regime (so-called Mira-type systems) from being the likely progenitor scenario for these SNe. Our model calculations are general, and can also be used for the subclass of SNe Ia that do show circumstellar interaction, e.g. the recent PTF 11kx. To constrain hydrogen in late-time spectra, we present ESO/VLT and ESO/New Technology Telescope optical and infrared observations of SNe Ia 1998bu and 2000cx in the nebular phase, 251-388 d after maximum. We see no signs of hydrogen line emission in SNe 1998bu and 2000cx at these epochs, and from the absence of Hα with a width of the order of ~10 3 km s –1 , we argue from modelling that the mass of such hydrogen-rich gas must be 0.03 M for both supernovae. Comparing similar upper limits with recent models of Pan et al., it seems that hydrogen-rich donors with a separation of 5 times the radius of the donor may be ruled out for the five SNe Ia 1998bu, 2000cx, 2001el, 2005am and 2005cf. Larger separation, helium-rich donors, or a double-degenerate origin for these supernovae seems more likely. Our models have also been used to put the limit on hydrogen-rich gas in the recent SN 2011fe, and for this supernova, a double-degenerate origin seems likely.

Description: We build differential-reddening maps for 66 Galactic globular clusters (GCs) with archival Hubble Space Telescope WFC/ACS F 606 W and F 814 W photometry. Because of the different GC sizes (characterized by the half-light radius R h ) and distances to the Sun, the WFC/ACS field of view (200 arcsec x 200 arcsec) coverage ( R obs ) lies in the range 1 R obs / R h 15 for about 85 per cent of the sample, with about 10 per cent covering only the inner ( R obs R h ) parts. We divide the WFC/ACS field of view across each cluster in a regular cell grid and extract the stellar-density Hess diagram from each cell, shifting it in colour and magnitude along the reddening vector until matching the mean diagram. Thus, the maps correspond to the internal dispersion of the reddening around the mean. Depending on the number of available stars (i.e. probable members with adequate photometric errors), the angular resolution of the maps range from 7 arcsec x 7 arcsec to 20 arcsec x 20 arcsec. We detect spatially variable extinction in the 66 GCs studied, with mean values ranging from 〈E(B-V)〉0.018 (NGC 6981) up to 〈E(B-V)〉0.016 (Palomar 2). Differential-reddening correction decreases the observed foreground reddening and the apparent distance modulus but, since they are related to the same value of E ( B  –  V ), the distance to the Sun is conserved. Fits to the mean-ridge lines of the highly extincted and photometrically scattered GC Palomar 2 show that age and metallicity also remain unchanged after the differential-reddening correction, but measurement uncertainties decrease because of the reduced scatter. The lack of systematic variations of 〈E(B-V)〉 with both the foreground reddening and the sampled cluster area indicates that the main source of differential reddening is interstellar.

Description: We present a physically motivated semi-analytic model to understand the clustering of high-redshift Lyman α emitters (LAEs). We show that the model parameters constrained by the observed luminosity functions can be used to predict large-scale bias and angular correlation function of LAEs. These predictions are shown to reproduce the observations remarkably well. We find that average masses of dark matter haloes hosting LAEs brighter than the threshold narrow-band magnitude ~25 are ~10 11 M . These are smaller than that of typical Lyman break galaxies (LBGs) brighter than a similar threshold continuum magnitude by a factor of ~10. This results in a smaller clustering strength of LAEs compared to LBGs. However, using the observed relationship between the UV continuum and Lyman α luminosity of LAEs, we show that both LAEs and LBGs belong to the same parent galaxy population with narrow-band techniques having greater efficiency in picking up galaxies with low UV luminosity. We also show that the lack of evidence for the presence of the one-halo term in the observed LAE angular correlation functions can be attributed to a sub-Poisson distribution of LAEs in dark matter haloes as a result of their low halo occupations.

Description: We present a detailed analysis of spectral line profiles in Type Ia supernova (SN Ia) spectra. We focus on the feature at ~3500–4000 Å, which is commonly thought to be caused by blueshifted absorption of Ca H&K. Unlike some other spectral features in SN Ia spectra, this feature often has two overlapping (blue and red) components. It is accepted that the red component comes from photospheric calcium. However, it has been proposed that the blue component is caused by either high-velocity calcium (from either abundance or density enhancements above the photosphere of the supernova, SN) or Si ii 3858. By looking at multiple data sets and model spectra, focusing on spectra near maximum brightness, we conclude that the blue component of the Ca H&K feature is caused by Si ii 3858 for most SNe Ia, although high-velocity calcium is likely important for some SNe. The strength of the Si ii 3858 feature varies strongly with the light-curve shape of an SN. As a result, the velocity measured from a single-Gaussian fit to the full line profile correlates with light-curve shape. The velocity of the Ca H&K component of the profile does not correlate with light-curve shape, contrary to previous claims. We detail the pitfalls of assuming that the blue component of the Ca H&K feature is caused by calcium, with implications for our understanding of SN Ia progenitors, explosions and cosmology.

Description: Subject of this paper is the statistical properties of ellipticity alignments between galaxies evoked by their coupled angular momenta. Starting from physical angular momentum models, we bridge the gap towards ellipticity correlations, ellipticity spectra and derived quantities such as aperture moments, comparing the intrinsic signals with those generated by gravitational lensing, with the projected galaxy sample of Euclid in mind. We investigate the dependence of intrinsic ellipticity correlations on cosmological parameters and show that intrinsic ellipticity correlations give rise to non-Gaussian likelihoods as a result of non-linear functional dependences. Comparing intrinsic ellipticity spectra to weak lensing spectra we quantify the magnitude of their contaminating effect on the estimation of cosmological parameters and find that biases on dark energy parameters are very small in an angular momentum-based model in contrast to the linear alignment model commonly used. Finally, we quantify whether intrinsic ellipticities can be measured in the presence of the much stronger weak lensing induced ellipticity correlations, if prior knowledge on a cosmological model is assumed.

Description: In this paper, I present a new method that has been developed for determining the brightness of a cloudless night sky, on the basis of widely available amateur observations of comets. The tests show the correctness of the method, which makes it possible to determine the level of light pollution, defined as the brightness of the artificial sky glow, through the use of the archival observations of comets. The use of data bases of comet observations in Poland in the period 1994–2009 has led to a positive verification of the known model map of the brightness of the night sky. Also, it has been possible to find changes in the level of light pollution in this period, at the selected observation sites.

Description: We present a complete sample of molecular clumps containing compact and ultracompact H ii (UC H ii ) regions between  = 10° and 60° and | b | 〈 1°, identified by combining the APEX Telescope Large Area Survey of the Galaxy submm and CORNISH radio continuum surveys with visual examination of archival infrared data. Our sample is complete to optically thin, compact and UC H ii regions driven by a zero-age main-sequence star of spectral type B0 or earlier embedded within a 1000 M clump. In total we identify 213 compact and UC H ii regions, associated with 170 clumps. Unambiguous kinematic distances are derived for these clumps and used to estimate their masses and physical sizes, as well as the Lyman continuum fluxes and sizes of their embedded H ii regions. We find a clear lower envelope for the surface density of molecular clumps hosting massive star formation of 0.05 g cm –2 , which is consistent with a similar sample of clumps associated with 6.7 GHz masers. The mass of the most massive embedded stars is closely correlated with the mass of their natal clump. Young B stars appear to be significantly more luminous in the ultraviolet than predicted by current stellar atmosphere models. The properties of clumps associated with compact and UC H ii regions are very similar to those associated with 6.7 GHz methanol masers and we speculate that there is little evolution in the structure of the molecular clumps between these two phases. Finally, we identify a significant peak in the surface density of compact and UC H ii -regions associated with the W49A star-forming complex, noting that this complex is truly one of the most massive and intense regions of star formation in the Galaxy.

Description: We present full Stokes radio polarization observations of the quasar PKS B2126–158 ( z  = 3.268) from 1 to 10 GHz using the Australia Telescope Compact Array. The source has large fractional circular polarization (CP), m c | V |/ I , detected at high significance across the entire band (from 15 to 90 per 128 MHz subband). This allows us to construct the most robust CP spectrum of an active galactic nucleus (AGN) jet to date. We find m c    +0.60 ± 0.03 from 1.5 to 6.5 GHz, with a peak of m c ~ 1 per cent before the spectrum turns over somewhere between 6.5 and 8 GHz, above which m c    –3.0 ± 0.4 . The fractional linear polarization (LP; p ) varies from 0.2 to ~1 per cent across our frequency range and is strongly anticorrelated with the fractional CP, with a best-fitting power law giving m c    p –0.24 ± 0.03 . This is the first clear relation between the observed LP and CP of an AGN jet, revealing the action of Faraday conversion of LP to CP within the jet. More detailed modelling in conjunction with high spatial resolution observations are required to determine the true driving force behind the conversion (i.e. magnetic twist or internal Faraday rotation). In particular determining whether the observed Faraday rotation is internal or entirely external to the jet is key to this goal. The simplest interpretation of our observations favours some internal Faraday rotation, implying that Faraday rotation-driven conversion of LP to CP is the dominant CP generation mechanism. In this case, a small amount of vector-ordered magnetic field along the jet axis is required, along with internal Faraday rotation from the low-energy end of the relativistic electron energy spectrum in an electron–proton-dominated jet.

Description: We present new H i observations of Hoag's Object (HO) obtained with the Westerbork Synthesis Radio Telescope. The data show that the luminous optical ring around the elliptical body has a bright H i counterpart that shares the kinematical properties of the optical ring. The entire H i structure is twice as large as the optical ring and shows a mild warp in its outer regions relative to the inner ring. We detect two additional H i sources close in redshift to that of HO, and report on a newly identified SDSS optical companion galaxy. The H i sources are ~0.3 and ~1 Mpc away in projected distance, and the companion galaxy is also ~1 Mpc away. Our main conclusion is that the H i detected in HO shows no indication that this galaxy has experienced a recent (less than ~1 Gyr ago) accretion event. At least one of the two additional H i detected objects does not have an optical counterpart. One possibility is that this object is an H i filament left over from an interaction shaping HO, in which case this interaction must also have occurred at least 1–2 Gyr ago.

Description: We report the first comparative study of strong Mg ii absorbers ( W r  ≥ 1.0 Å) seen towards radio-loud quasars of core-dominated (CDQ) and lobe-dominated (LDQ) types and normal quasars (QSOs). The CDQ and LDQ samples were derived from the Sloan Digital Sky Survey Data Release 7 after excluding known ‘broad-absorption-line’ quasars and blazars. The Mg ii associated absorption systems having a velocity offset v  〈 5000 km s –1 from the systemic velocity of the background quasar were also excluded. Existing spectroscopic data for redshift-matched sightlines of 3975 CDQs and 1583 LDQs, covering an emission redshift range 0.39–4.87, were analysed and 864 strong Mg ii absorbers were found, covering the redshift range 0.45–2.17. The conclusions reached using this well-defined large data set of strong Mg ii absorbers are (i) the number density, d N /d z , towards CDQs shows a small, marginally significant excess (~9 per cent at 1.5 significance) over the estimate available for QSOs; (ii) in the redshift space, this difference is reflected in terms of a 1.6 excess of d N /d z over the QSOs, within the narrow redshift interval 1.2–1.8; (iii) the d N /dβ distribution (with β =  v / c ) for CDQs shows a significant excess (at 3.75 level) over the distribution found for a redshift- and luminosity-matched sample of QSOs, at β in the range 0.05–0.1. This leads us to infer that a significant fraction of strong Mg ii absorption systems seen in this offset velocity range are probably associated with the CDQs and might be accelerated into the line of sight by their powerful jets and/or due to the accretion-disc outflows close to our direction. Support to this scenario comes from a consistency check in which we consider only the spectral range corresponding to β 〉 0.2. The computed redshift distribution for strong Mg ii absorbers towards CDQs now shows excellent agreement with that known for QSOs, as indeed is expected for purely intervening absorption systems. Thus, it appears that for CDQs (and blazars) the associated strong Mg ii absorbers can be seen at much larger velocities relative to the nucleus than the commonly adopted upper limit of 5000 km s –1 .

Description: Dynamics of a complete sample of small perihelion distance near-parabolic comets discovered in the years 2006–2010 are studied (i.e. of 22 comets of q osc  〈 3.1 au). First, osculating orbits are obtained after a very careful positional data inspection and processing, including where appropriate, the method of data partitioning for determination of pre- and post-perihelion orbit for tracking then its dynamical evolution. The non-gravitational acceleration in the motion is detected for 50 per cent of investigated comets, in a few cases for the first time. Different sets of non-gravitational parameters are determined from pre- and post-perihelion data for some of them. The influence of the positional data structure on the possibility of the detection of non-gravitational effects and the overall precision of orbit determination is widely discussed. Secondly, both original and future orbits were derived by means of numerical integration of swarms of virtual comets obtained using a Monte Carlo cloning method. This method allows us to follow the uncertainties of orbital elements at each step of dynamical evolution. The complete statistics of original and future orbits that includes significantly different uncertainties of 1/ a -values is presented, also in the light of our results obtained earlier. Basing on 108 comets examined by us so far, we conclude that only one of them, C/2007 W1 Boattini, seems to be a serious candidate for an interstellar comet. We also found that 53 per cent of 108 near-parabolic comets escaping in the future from the Solar system, and the number of comets leaving the Solar system as so called Oort spike comets (i.e. comets suffering very small planetary perturbations) is 14 per cent. A new method for cometary orbit quality assessment is also proposed by means of modifying the original method, introduced by Marsden, Sekanina & Everhart. This new method leads to a better diversification of orbit quality classes for contemporary comets.

Description: We present the chemical abundance measurements of the first large, medium-resolution, uniformly selected damped Lyman α system (DLA) survey. The sample contains 99 DLAs towards 89 quasars selected from the SDSS DR5 DLA sample in a uniform way. We analyse the metallicities and kinematic diagnostics, including the velocity width of 90 per cent of the optical depth, v 90 , and the equivalent widths of the Si ii 1526 ( W 1526 ), C iv 1548 and Mg ii 2796 transitions. To avoid strong line-saturation effects on the metallicities measured in medium-resolution spectra (FWHM ~ 71 km s –1 ), we derived metallicities from metal transitions which absorbed at most 35 per cent of the quasar continuum flux. We find the evolution in cosmic mean metallicity of the sample, 〈 Z 〉 = (–0.04 ± 0.13) z  – (1.06 ± 0.36), consistent with no evolution over the redshift range z ~ [2.2, 4.4], but note that the majority of our sample falls at z ~ [2.2, 3.5]. The apparent lack of metallicity evolution with redshift is also seen in a lack of evolution in the median v 90 and W 1526 values. While this result may seem to conflict with other large surveys that have detected significant metallicity evolution, such as Rafelski et al. who found 〈 Z 〉 = (–0.22 ± 0.03) z  – (0.65 ± 0.09) over z ~ [0, 5], several tests show that these surveys are not inconsistent with our new result. However, over the smaller redshift range covered by our uniformly selected sample, the true evolution of the cosmic mean metallicity in DLAs may be somewhat flatter than the Rafelski et al. estimate.

Description: Expulsion of neutron-rich matter following the merger of neutron star binaries is crucial to the radioactively powered electromagnetic counterparts of these events and to their relevance as sources of r -process nucleosynthesis. Here we explore the long-term (viscous) evolution of remnant black hole accretion discs formed in such mergers by means of two-dimensional, time-dependent hydrodynamical simulations. The evolution of the electron fraction due to charged-current weak interactions is included, and neutrino self-irradiation is modelled as a lightbulb that accounts for the disc geometry and moderate optical depth effects. Over several viscous times (~1 s), a fraction of ~10 per cent of the initial disc mass is ejected as a moderately neutron-rich wind ( Y e  ~ 0.2) powered by viscous heating and nuclear recombination, with neutrino self-irradiation playing a sub-dominant role. Although the properties of the outflow vary in time and direction, their mean values in the heavy-element production region are relatively robust to variations in the initial conditions of the disc and the magnitude of its viscosity. The outflow is sufficiently neutron-rich that most of the ejecta forms heavy r -process elements with mass number A   130, thus representing a new astrophysical source of r -process nucleosynthesis, distinct from that produced in the dynamical ejecta. Due to its moderately high entropy, disc outflows contain a small residual fraction ~1 per cent of helium, which could produce a unique spectroscopic signature.

Description: We have performed multiband UBVR C I C JHK S photometry of two young clusters located at large Galactocentric distances in the direction of the Perseus spiral arm. The obtained distances and colour excesses amount to 3.9 ± 0.11 kpc, E ( B  –  V ) = 0.62 ± 0.05 for Berkeley 94, and 4.3 ± 0.15 kpc, E ( B  –  V ) = 0.58 ± 0.06 for Berkeley 96. The respective ages, as measured from the comparison of the upper colour–magnitude diagrams to model isochrones, amount to log 10 Age(yr) = 7.5 ± 0.07 and 7.0 ± 0.07, respectively. A sequence of optical pre-main-sequence (PMS) members is proposed in both clusters. In addition, samples of objects showing ( H  –  K S ) excess are found. Part of these are suggested to be PMS cluster members of lower mass than the optical candidates. The spatial distribution of these sources, the comparison to Galactic models and to the expected number of contaminating distant red galaxies, and the spectral energy distribution in particular cases support this suggestion. The spatial distributions shown by members in different mass ranges can be interpreted in terms of the results from numerical simulations. According to these, different initial conditions and evolutionary dynamical paths are suggested for the clusters. Berkeley 94 would have formed under supervirial conditions, and followed the so-called warm collapse model in its evolution, whereas Berkeley 96 would have formed with a subvirial structure, and would have evolved following a cold collapse path. Both processes would be able to reproduce the suggested degree of mass segregation and their spatial distribution by mass range. Finally, the mass distributions of the clusters, from the most massive stars down to PMS stars around 1.3 M , are calculated. An acceptable general agreement with the Salpeter initial mass function slope is found.

Description: The class of tidal features around galaxies known as ‘shells’ or ‘umbrellas’ comprises debris that has arisen from high-mass-ratio mergers with low-impact parameter; the nearly radial orbits of the debris give rise to a unique morphology, a universal density profile and a tight correlation between positions and velocities of the material. As such they are accessible to analytical treatment, and can provide a relatively clean system for probing the gravitational potential of the host galaxy. In this work, we present a simple analytical model that describes the density profile, phase-space distribution, and geometry of a shell and whose parameters are directly related to physical characteristics of the interacting galaxies. The model makes three assumptions: the orbit of the interacting galaxies is radial, the potential of the host galaxy at the shell radius is spherical and the satellite galaxy's initial velocity distribution is Maxwellian. We quantify the error introduced by the first two assumptions and show that selecting shells by their appearance on the sky is a sufficient basis to assume that these simplifications are valid. We further demonstrate that (1) given only an image of a shell, the radial gravitational force at the shell edge and the phase-space density of the satellite are jointly constrained, (2) combining the image with measurements of either point line-of-sight velocities or integrated-light spectra will yield an independent estimate of the gravitational force at a shell and (3) an independent measurement of this force is obtained for each shell observed around a given galaxy, potentially enabling a determination of the galactic mass distribution.

Description: In the context of upcoming large-scale structure surveys such as Euclid , it is of prime importance to quantify the effect of peculiar velocities on geometric probes. Hence, the formalism to compute in redshift space the geometrical and topological one-point statistics of mildly non-Gaussian 2D and 3D cosmic fields is developed. Leveraging the partial isotropy of the target statistics, the Gram–Charlier expansion of the joint probability distribution of the field and its derivatives is reformulated in terms of the corresponding anisotropic variables. In particular, the cosmic non-linear evolution of the Minkowski functionals, together with the statistics of extrema, is investigated in turn for 3D catalogues and 2D slabs. The amplitude of the non-Gaussian redshift distortion correction is estimated for these geometric probes. In 3D, gravitational perturbation theory is implemented in redshift space to predict the cosmic evolution of all relevant Gram–Charlier coefficients. Applications to the estimation of the cosmic parameters ( z ) and β =  f / b 1 from upcoming surveys are discussed. Such statistics are of interest for anisotropic fields beyond cosmology.

Description: One of the most promising ways to study the epoch of reionization (EoR) is through radio observations of the redshifted 21-cm line emission from neutral hydrogen. These observations are complicated by the fact that the mapping of redshifts to line-of-sight positions is distorted by the peculiar velocities of the gas. Such distortions can be a source of error if they are not properly understood, but they also encode information about cosmology and astrophysics. We study the effects of redshift space distortions on the power spectrum of 21-cm radiation from the EoR using large-scale N -body and radiative transfer simulations. We quantify the anisotropy introduced in the 21-cm power spectrum by redshift space distortions and show how it evolves as reionization progresses and how it relates to the underlying physics. We go on to study the effects of redshift space distortions on LOFAR observations, taking instrument noise and foreground subtraction into account. We find that LOFAR should be able to directly observe the power spectrum anisotropy due to redshift space distortions at spatial scales around k  ~ 0.1 Mpc –1 after 1000 h of integration time. At larger scales, sample errors become a limiting factor, while at smaller scales detector noise and foregrounds make the extraction of the signal problematic. Finally, we show how the astrophysical information contained in the evolution of the anisotropy of the 21-cm power spectrum can be extracted from LOFAR observations, and how it can be used to distinguish between different reionization scenarios.

Description: Among the three cosmological enigma solved by the theory of inflation, viz. (a) large-scale flatness, (b) absence of monopoles and strings and (c) structure formation, the first two are addressed from the viewpoint of the observed scales having originated from very small ones, on which the density fluctuations of the curvaton and relics are inevitably of the order of unity or larger. By analysing strictly classically (and in two different gauges to ensure consistency) the density evolution of the smoothest possible pre-inflationary component – thermal radiation – it is found that the O(1) statistical fluctuations on the thermal wavelength scale present formidable obstacles to the linear theory of amplitude growth by the end of inflation. Since this wavelength scale exited the horizon at an early stage of inflation, it severely limits the number of e-folds of perturbative inflation. With more e-folds than 60 there will be even larger fluctuations in the radiation density that ensures inflation keeps making ‘false starts’. The only ‘way out’ is to invoke a super-homogeneous pre-inflationary fluid, at least on small scales, adding to the fine-tuning and preventing one from claiming that inflation simply ‘redshifts away’ all the relic inhomogeneities; i.e. the theory actually provided no explanation of (a) or (b), merely a tautology.

Description: Recently, a comparison between the locations of 6.7-GHz methanol masers and dust continuum emission has renewed speculation that these masers can be associated with evolved stars. The implication of such a scenario would be profound, especially for the interpretation of large surveys for 6.7-GHz masers, individual studies where high-mass star formation has been inferred from the presence of 6.7-GHz methanol masers and for the pumping mechanisms of these masers. We have investigated the two instances where 6.7-GHz methanol masers have been explicitly suggested to be associated with evolved stars, and we find the first to be associated with a standard high-mass star formation region, and the second to be a spurious detection. We also find no evidence to suggest that the methanol maser action can be supported in the environments of evolved stars. We thereby confirm their exclusive association with high-mass star formation regions.

Description: 14 stars from a sample of Magellanic Cloud objects selected to have a mid-infrared flux excess have been found to also show TiO bands in emission. The mid-infrared dust emission and the TiO band emission indicate that these stars have large amounts of hot circumstellar dust and gas in close proximity to the central star. The luminosities of the sources are typically several thousand L , while the effective temperatures are ~4000–8000 K which puts them bluewards of the giant branch. Such stars could be post-asymptotic giant branch (post-AGB) stars of mass ~0.4–0.8 M or pre-main-sequence stars (young stellar objects) with masses in the range ~7–19 M . If the stars are pre-main-sequence stars, they are substantially cooler and younger than stars at the birth line where Galactic protostars are first supposed to become optically visible out of their molecular clouds. They should therefore be hidden in their present evolutionary state, although this problem may be overcome if asymmetries are invoked or if the reduced metallicity of the Small Magellanic Cloud and Large Magellanic Cloud compared to the Galaxy makes the circumstellar material more transparent. The second explanation for these stars is that they are post-AGB or post-red giant branch stars that have recently undergone a binary interaction when the red giant of the binary system filled its Roche lobe. Being oxygen-rich, they have gone through this process before becoming carbon stars. Most of the stars vary slowly on time-scales of 1000 d or more, suggesting a changing circumstellar environment. Apart from the slow variations, most stars also show variability with periods of tens to hundreds of days. One star shows a period that is rapidly decreasing and we speculate that this star may have accreted a large blob of gas and dust on to a disc whose orbital radius is shrinking rapidly. Another star has Cepheid-like pulsations of rapidly increasing amplitude, suggesting a rapid rate of evolution. Seven stars show quasi-periodic variability and one star has a light curve similar to that of an eclipsing binary.

Description: Faint undetected sources of radio-frequency interference (RFI) might become visible in long radio observations when they are consistently present over time. Thereby, they might obstruct the detection of the weak astronomical signals of interest. This issue is especially important for Epoch of Reionization (EoR) projects that try to detect the faint redshifted H  i signals from the time of the earliest structures in the Universe. We explore the RFI situation at 30–163 MHz by studying brightness histograms of visibility data observed with Low-Frequency Array (LOFAR), similar to radio-source-count analyses that are used in cosmology. An empirical RFI distribution model is derived that allows the simulation of RFI in radio observations. The brightness histograms show an RFI distribution that follows a power-law distribution with an estimated exponent around –1.5. With several assumptions, this can be explained with a uniform distribution of terrestrial radio sources whose radiation follows existing propagation models. Extrapolation of the power law implies that the current LOFAR EoR observations should be severely RFI limited if the strength of RFI sources remains strong after time integration. This is in contrast with actual observations, which almost reach the thermal noise and are thought not to be limited by RFI. Therefore, we conclude that it is unlikely that there are undetected RFI sources that will become visible in long observations. Consequently, there is no indication that RFI will prevent an EoR detection with LOFAR.

Description: Very Large Array deep radio images at 1.4 GHz in total intensity and polarization reveal a diffuse non-thermal source in the interacting clusters A3411–A3412. Moreover, a small-size low-power radio halo at the centre of the merging cluster A3411 is found. We present here new optical and X-ray data and discuss the nature and properties of the diffuse non-thermal source. We suggest that the giant diffuse radio source is related to the presence of a large-scale filamentary structure and to multiple mergers in the A3411–A3412 complex.

Description: We describe a 325-MHz survey, undertaken with the Giant Metrewave Radio Telescope (GMRT), which covers a large part of the three equatorial fields at 9, 12 and 14.5 h of right ascension from the Herschel -Astrophysical Terahertz Large Area Survey (H-ATLAS) in the area also covered by the Galaxy And Mass Assembly (GAMA) survey. The full data set, after some observed pointings were removed during the data reduction process, comprises 212 GMRT pointings covering ~90 deg 2 of sky. We have imaged and catalogued the data using a pipeline that automates the process of flagging, calibration, self-calibration and source detection for each of the survey pointings. The resulting images have resolutions of between 14 and 24 arcsec and minimum rms noise (away from bright sources) of ~1 mJy beam –1 , and the catalogue contains 5263 sources brighter than 5. We investigate the spectral indices of GMRT sources which are also detected at 1.4 GHz and find them to agree broadly with previously published results; there is no evidence for any flattening of the radio spectral index below S 1.4  = 10 mJy. This work adds to the large amount of available optical and infrared data in the H-ATLAS equatorial fields and will facilitate further study of the low-frequency radio properties of star formation and AGN activity in galaxies out to z  ~ 1.

Description: We demonstrate a new multiwavelength technique for two-dimensional parametric modelling of galaxy surface-brightness profiles, which we have incorporated into the widely used software galfit . Our new method, named galfitm , extends galfit3 's current single-band fitting process by simultaneously using multiple images of the same galaxy to constrain a wavelength-dependent model. Each standard profile parameter may vary as a function of wavelength, with a user-definable degree of smoothness, from constant to fully free. The performance of galfitm is evaluated by fitting elliptical Sérsic profiles to ugriz imaging data for 4026 galaxies, comprising the original Sloan Digital Sky Survey (SDSS) imaging for 163 low-redshift ( v 7000 km s –1 ) galaxies and 3863 artificially redshifted (0.01 z 0.25) images of the same galaxies. Comparing results from single-band and multiband techniques, we show that galfitm significantly improves the extraction of information, particularly from bands with low signal-to-noise ratio (e.g. u and z SDSS bands) when combined with higher signal-to-noise images. We also study systematic trends in the recovered parameters, particularly Sérsic index, that appear when one performs measurements of the same galaxies at successively higher redshifts. We argue that it is vital that studies investigating the evolution of galaxy structure are careful to avoid or correct for these biases. The resulting multiband photometric structural parameters for our sample of 163 galaxies are provided. We demonstrate the importance of considering multiband measurements by showing that the Sérsic indices of spiral galaxies increase to redder wavelengths, as expected for composite bulge–disc systems. Finally, for the ellipticals in our sample, which should be well represented by single-Sérsic models, we compare our measured parameters to those from previous studies.

Description: Motivated by the recent report of the detailed spectra of IC 443 and W44 based on four years of observations with the Fermi Large Area Telescope, -rays produced via proton–proton interaction in the two supernova remnants (SNRs) have been investigated in the diffusive shock acceleration scenario. In the model, a part of the SNR shell transporting into ambient dense molecular clouds (MCs), and a shock with a relatively low Alfvén Mach number can be produced. Relativistic protons are accelerated in the shock via the diffusive acceleration process; moreover, a break in the particle distribution is induced since the damping of Alfvén waves when the shock transporting into partly ionized plasma. A spectrum of the accelerated protons in the shock can be obtained in the test-particle case, taking into account the effect of the ambient partly ionized plasma on the acceleration process. Furthermore, hadronic -rays with a peak around several GeVs are reproduced as the protons inelastically colliding with the ambient matter of the crushed gas. The observed -ray spectral distributions of the SNR IC 443 and W44 can be successfully reproduced using the static model in the test-particle scenario. It can be concluded that the observed -rays can be explained in the diffusive shock case as the shock waves transporting into the dense MCs for the two remnants.

Description: We present a clustering analysis of X-ray selected active galactic nuclei (AGN) by compiling X-ray samples from the literature and re-estimating the dark-matter (DM) halo masses of AGN in a uniform manner. We find that moderate-luminosity AGN ( L 2–10 keV  ~= 10 42 –10 44 erg s –1 ) in the z  ~= 0–1.3 Universe are typically found in DM haloes with masses of ~10 13 M . We then compare our findings to the theoretical predictions of the coupled galaxy and black hole formation model galform . We find good agreement when our calculation includes the hot-halo mode of accretion on to the central black hole. This type of accretion, which is additional to the common cold accretion during disc instabilities and galaxy mergers, is tightly coupled to the AGN feedback in the model. The hot-halo mode becomes prominent in DM haloes with masses greater than ~10 12.5 M , where AGN feedback typically operates, giving rise to a distinct class of moderate-luminosity AGN that inhabit rich clusters and superclusters. Cold gas fuelling of the black hole cannot produce the observationally inferred DM halo masses of X-ray AGN. Switching off AGN feedback in the model results in a large population of luminous quasars ( L 2–10 keV  〉 10 44 erg s –1 ) in DM haloes with masses up to ~10 14 M , which is inconsistent with the observed clustering of quasars. The abundance of hot-halo AGN decreases significantly in the z ~= 3–4 universe. At such high redshifts, the cold accretion mode is solely responsible for shaping the environment of moderate-luminosity AGN. Our analysis supports two accretion modes (cold and hot) for the fuelling of supermassive black holes and strongly underlines the importance of AGN feedback in cosmological models both of galaxy formation and black hole growth.

Description: A major stage of radio interferometric data processing is calibration or the estimation of systematic errors in the data and the correction for such errors. A stochastic error (noise) model is assumed, and in most cases, this underlying model is assumed to be Gaussian. However, outliers in the data due to interference or due to errors in the sky model would have adverse effects on processing based on a Gaussian noise model. Most of the shortcomings of calibration such as the loss in flux or coherence, and the appearance of spurious sources, could be attributed to the deviations of the underlying noise model. In this paper, we propose to improve the robustness of calibration by using a noise model based on Student's t -distribution. Student's t -noise is a special case of Gaussian noise when the variance is unknown. Unlike Gaussian-noise-model-based calibration, traditional least-squares minimization would not directly extend to a case when we have a Student's t -noise model. Therefore, we use a variant of the expectation–maximization algorithm, called the expectation–conditional maximization either algorithm, when we have a Student's t -noise model and use the Levenberg–Marquardt algorithm in the maximization step. We give simulation results to show the robustness of the proposed calibration method as opposed to traditional Gaussian-noise-model-based calibration, especially in preserving the flux of weaker sources that are not included in the calibration model.

Description: A single open magnetic flux tube spanning the solar photosphere (solar radius ~= R ) and the lower corona (R  + 10 Mm) is modelled in magnetohydrostatic equilibrium within a realistic stratified atmosphere subject to solar gravity. Such flux tubes are observed to remain relatively stable for up to a day or more, and it is our aim to apply the model as the background condition for numerical studies of energy transport mechanisms from the surface to the corona. We solve analytically an axially symmetric 3D structure for the model, with magnetic field strength, plasma density, pressure and temperature all consistent with observational and theoretical estimates. The self-similar construction ensures the magnetic field is divergence free. The equation of pressure balance for this particular set of flux tubes can be integrated analytically to find the pressure and density corrections required to preserve the magnetohydrostatic equilibrium. The model includes a number of free parameters, which makes the solution applicable to a variety of other physical problems and it may therefore be of more general interest.

Description: We report photometric detections of orbital and superorbital signals, and negative orbital sidebands, in the light curves of the nova-like cataclysmic variables AQ Mensae and IM Eridani. The frequencies of the orbital, superorbital and sideband signals are 7.0686 (3), 0.263 (3) and 7.332 (3) cycles d –1 (c d –1 ) in AQ Mensae, and 6.870 (1), 0.354 (7) and 7.226 (1) c d –1 in IM Eridani. We also find a spectroscopic orbital frequency in IM Eridani of 6.86649 (2) c d –1 . These observations can be reproduced by invoking an accretion disc that is tilted with respect to the orbital plane. This model works well for X-ray binaries, in which irradiation by a primary neutron star can account for the disc's tilt. A likely tilt mechanism has yet to be identified in CVs, yet the growing collection of observational evidence indicates that the phenomenon of tilt is indeed at work in this class of object. The results presented in this paper bring the number of CVs known to display signals associated with retrograde disc precession to 12. We also find AQ Men to be an eclipsing system. The eclipse depths are highly variable, which suggests that the eclipses are grazing. This finding raises the possibility of probing variations in disc tilt by studying systematic variations in the eclipse profile.

Description: We investigate the onset of pressure-driven toroidal-mode instabilities in accretion mounds on neutron stars by 3D magnetohydrodynamic (MHD) simulations using the pluto MHD code. Our results confirm that for mounds beyond a threshold mass, instabilities form finger-like channels at the periphery, resulting in mass-loss from the magnetically confined mound. Ring-like mounds with hollow interior show the instabilities at the inner edge as well. We perform the simulations for mounds of different sizes to investigate the effect of the mound mass on the growth rate of the instabilities. We also investigate the effect of such instabilities on observables such as cyclotron resonant scattering features and timing properties of such systems.

Description: External fields in Milgromian dynamics (MD or MOND) break the Strong Equivalence Principle (SEP) and change the dynamics of self-bound stellar systems moving in space-varying background gravitational fields. We study two kinds of re-virialization of the stellar systems: the violent phase transition and the adiabatic phase transition for systems moving on radial orbits, where the external field evolves from strong to weak and whose corresponding dynamics change from Newtonian to Milgromian. We find that the time-scale for the phase transformation from Newtonian to Milgromian gravity lies only within one to a few crossing times for low-density globular clusters with masses ranging from 10 4 M to 10 6 M . Thus, a globular cluster can appear frozen in the Newtonian regime despite being in the Milgromian regime for not longer than a few crossing times. We also study the kinematics and anisotropy profiles of the systems. The velocity dispersions of the systems are larger after the phase transitions, especially for the outer regions of the stellar systems. Moreover, the isotropic systems become radially anisotropic, especially for the outer parts, after the process caused by the dynamical phase transition. Deeper Milgromian systems have more radially anisotropic velocity dispersion functions. We also find that the final profiles of density, velocity dispersion and anisotropy do not depend on the details of the phase transition. That is, the mass distribution and kinematics of the end-states of the globular clusters do not depend on the rapidity of the transition from Newtonian to Milgromian gravity. Thus, the transition from the Newtonian to the Milgromian regime naturally induces a significant radially anisotropic velocity distribution in a globular cluster.

Description: Using a fast semi-analytic raytracing code, we study the variability of relativistically broadened Fe–Kα lines due to discoseismic oscillations concentrated in the innermost regions of accretion discs around black holes. The corrugation mode, or c-mode, is of particular interest as its natural frequency corresponds well to the ~0.1–15 Hz range observed for low-frequency quasi-periodic oscillations (LFQPOs) for lower spins. Comparison of the oscillation phase dependent variability and quasi-periodic oscillation-phase stacked Fe–Kα line observations will allow such discoseismic models to be confirmed or ruled out as a source of particular LFQPOs. The spectral range and frequency of the variability of the Fe–Kα line due to c-modes can also potentially be used to constrain the black hole spin if observed with sufficient temporal and spectral resolution.

Description: We present and discuss accurate and densely mapped BVR C I C light curves of the neon Nova Mon 2012, supplemented by the evolution in Stromgren b and y bands and in the integrated flux of relevant emission lines. Our monitoring started with the optical discovery of the nova (50 days past the first detection in gamma-rays by Fermi -LAT) and extend to day +270, well past the end of the super-soft phase in X-rays. The nova was discovered during the nebular decline, well past t 3 and the transition to optically thin ejecta. It displayed very smoothly evolving light curves. A bifurcation between y and V light curves took place at the start of the super-soft X-ray source (SSS) phase, and a knee developed towards the end of the SSS phase. The apparent magnitude of the nova at the unobserved optical maximum is constrained to +3 ≤  V  ≤ 4.5. The appearance, grow in amplitude and then demise of a 0.29585 (±0.00002) days orbital modulation of the optical brightness was followed along the nova evolution. The observed modulation, identical in phase and period with the analogue seen in the X-ray and satellite ultraviolet, has a near-sinusoidal shape and a weak secondary minimum at phase 0.5. We favour an interpretation in terms of super-imposed ellipsoidal distortion of the Roche lobe filling companion and irradiation of its side facing the WD. Similar light curves are typical of symbiotic stars where a Roche lobe filling giant is irradiated by a very hot WD. Given the high orbital inclination, mutual occultation between the donor star and the accretion disc could contribute to the observed modulation. The optical+infrared spectral energy distribution of Nova Mon 2012 during the quiescence preceding outburst is nicely fitted by an early K-type main-sequence star (~K3V) at 1.5 kpc distance, reddened by E ( B  –  V ) = 0.38, with a WD companion and an accretion disc contributing to the observed blue excess and moderate Hα emission. A typical early K-type main-sequence star with a mass of ~0.75 M and a radius of ~0.8 R would fill its Roche lobe for a P  = 0.29585 d orbital period and a more massive WD companion (as implied by the large Ne overabundance of the ejecta).

Description: The redshift dependence of the abundance of galaxy clusters is very sensitive to the statistical properties of primordial density perturbations. It can thus be used to probe small deviations from Gaussian initial conditions. Such deviations constitute a very important signature of many inflationary scenarios, and are thus expected to provide crucial information on physical processes which took place in the very early Universe. We have determined the biases which may be introduced in the estimation of cosmological parameters by wrongly assuming the absence of primordial non-Gaussianities. Although we find that the estimation of the present-day dark energy density using cluster counts is not very sensitive to the non-Gaussian properties of the density field, we show that the biases can be considerably larger in the estimation of the dark energy equation of state parameter w and of the amplitude of the primordial density perturbations. Our results suggest that a significant level of non-Gaussianity at cluster scales may be able to reconcile the constraint on the amplitude of the primordial perturbations obtained using galaxy cluster number counts from the Planck Sunyaev–Zeldovich Catalog with that obtained from the primary cosmic microwave background anisotropies measured by the Planck satellite.

Description: We report results from our 1D radiative transfer modelling of dust in the hydrogen-deficient planetary nebula IRAS 18333–2357 located in the globular cluster M22. A spectral energy distribution was constructed from archival UV, optical and IR data including Akari photometry at its 18, 65, 90, 140 and 160 μm bands. An archival Spitzer spectrum shows several aromatic infrared bands indicating a carbon-rich dust shell. The spectral energy distribution is well fitted by a model which considers a modified Mathis–Rumpl–Nordsieck grain size distribution and a radial density function which includes compression of the nebula by its interaction with the Galactic halo gas. The model indicates that a significant amount of cold dust, down to a temperature of 50 K, is present at the outer edge of the nebula. At the inner edge, the dust temperature is 97 K. The dust shell has a size of 26 ± 6.3 arcsec. We find a large amount of excess emission, over the emission from thermal equilibrium dust, in the mid-IR region. This excess emission may have originated from the thermally fluctuating dust grains with size ~12 Å in the UV field of the hot central star. These grains, however, come from the same population and conditions as the thermal equilibrium grains. The dust mass of this grain population is (1.2 ± 0.73) 10 –3 M and for the thermal equilibrium grains it is (1.4 ± 0.60) 10 –4 M , leading to a total dust mass of (1.3 ± 0.91) 10 –3 M . The derived dust-to-gas mass ratio is 0.3 ± 0.21. For a derived bolometric luminosity of (1700 ± 1230) L and an assumed central star mass of (0.55 ± 0.02) M , the surface gravity is derived to be log g  = 4.6 ± 0.24. We propose that the progenitor of IRAS 18333–2357 had possibly evolved from an early stellar merger case and the hydrogen-deficient nebula results from a late thermal pulse. The hydrogen-rich nebula, which was ejected by the progenitor during its normal asymptotic giant branch evolution, might have been stripped off by its strong interaction with the Galactic halo gas.

Description: We analyse the evolution of colour gradients predicted by the hydrodynamical models of early-type galaxies (ETGs) in Pipino et al., which reproduce fairly well the chemical abundance pattern and the metallicity gradients of local ETGs. We convert the star formation (SF) and metal content into colours by means of stellar population synthetic model and investigate the role of different physical ingredients, as the initial gas distribution and content, and SF , i.e. the normalization of SF rate. From the comparison with high-redshift data, a full agreement with optical rest-frame observations at z   1 is found, for models with low SF , whereas some discrepancies emerge at 1 〈  z  〈 2, despite our models reproduce quite well the data scatter at these redshifts. To reconcile the prediction of these high SF systems with the shallower colour gradients observed at lower z we suggest intervention of one to two dry mergers. We suggest that future studies should explore the impact of wet galaxy merging, interactions with environment, dust content and a variation of the initial mass function from the galactic centres to the peripheries.

Description: The interaction between a planet located in the inner region of a disc and the warped outer region is studied. We consider the stage of evolution after the planet has cleared-out a gap, so that the planetary orbit evolves only under the gravitational potential from the disc. We develop a secular analysis and compute the evolution of the orbital elements by solving Lagrange's equations valid to second order in the eccentricity. We also perform numerical simulations with the full disc potential. In general, the interaction between the disc and the planet leads to the precession of the orbit. The orbital plane therefore becomes tilted relative to the disc's inner parts, with no change in the eccentricity. When the inclination approaches 90°, there is an instability and the eccentricity increases. In this case, both the inclination and the eccentricity develop large variations, with the orbit becoming retrograde. As the eccentricity reaches high values, we would expect tidal capture on a short orbit of the planet by the star to occur. This instability happens when the disc is severely warped, or if there is a significant amount of mass in a ring inclined by at least 45° relative to the initial orbital plane. The inclination of the orbit does not depend on the semimajor axis nor on the planet's mass. However, for a significant inclination to be generated on a time-scale of at most a few Myr, the planet should be beyond the snow line. The process described here would therefore produce two distinct populations of inclined planets: one with objects beyond the snow line with at most moderate eccentricities, and another with objects on short circularized orbits.

Description: Hubble Space Telescope observations of globular clusters (GCs) in the Antennae galaxy show clusters of clusters, or regions in the galaxy that span hundreds of parsec, where many of the GCs are doomed to collide, and eventually merge. Several such objects appear likely to present a significant range in ages, hence possibly metallicities, and their merger could plausibly lead to multimetallic GCs. Here we explore this process with direct-summation N -body simulations with graphics processing unit hardware. Our results reveal that colliding GCs with different metallicities and ages can produce a GC with multiplicity and occupation fractions not unlike those observed in multimetallic clusters. In our simulations, the merged clusters have a phase with a larger amount of flattening than average, as a consequence of rapid rotation – thus suggesting that relatively recent mergers may play a role in producing highly flattened, multimetallic clusters. We additionally explore the role of the King parameter of the cluster in the occupation fractions with a set of 160 direct-summation simulations and find that for equal size clusters the King parameter of the progenitor clusters determines the occupation fractions in the merger product, while in unequal size mergers the size of the clusters dominates the distribution of stars in the new GC. In particular, we find that the observed distribution of populations in  Cen can be described to some extent with our dynamical models.

Description: We present a simulation analysis of weak gravitational lensing flexion and shear measurement using shapelet decomposition, and identify differences between flexion and shear measurement noise in deep survey data. Taking models of galaxies from the Hubble Space Telescope Ultra Deep Field (HUDF) and applying a correction for the HUDF point spread function, we generate lensed simulations of deep, optical imaging data from Hubble's Advanced Camera for Surveys, with realistic galaxy morphologies. We find that flexion and shear estimates differ in our measurement pipeline: whereas intrinsic galaxy shape is typically the dominant contribution to noise in shear estimates, pixel noise due to finite photon counts and detector read noise is a major contributor to uncertainty in flexion estimates, across a broad range of galaxy signal-to-noise. This pixel noise also increases more rapidly as galaxy signal-to-noise decreases than is found for shear estimates. We provide simple power-law fitting functions for this behaviour, for both flexion and shear, allowing the effect to be properly accounted for in future forecasts for flexion measurement. Using the simulations, we also quantify the systematic biases of our shapelet flexion and shear measurement pipeline for deep Hubble data sets such as Galaxy Evolution from Morphology and SEDs, Space Telescope A901/902 Galaxy Evolution Survey or Cosmic Evolution Survey. Flexion measurement biases are found to be significant but consistent with previous studies.

Description: We use an adaptation of the BzK s technique to select ~40 000 z  ~ 2 galaxies (to K AB = 24), including ~5000 passively evolving (PE) objects (to K AB = 23), from 2.5 deg 2 of deep Canada–France–Hawaii Telescope (CFHT) imaging. The passive galaxy luminosity function (LF) exhibits a clear peak at R  = 22 and a declining faint-end slope ( $\alpha = -0.12 ^{+0.16}_{-0.14}$ ), while that of star-forming galaxies is characterized by a steep faint-end slope [ $\alpha = -1.43\pm 0.02({\rm systematic})^{+0.05}_{-0.04}({\rm random})$ ]. The details of the LFs are somewhat sensitive (at the 〈25 per cent level) to cosmic variance even in these large (~0.5 deg 2 ) fields, with the D2 field (located in the Cosmological Evolution Survey, COSMOS field) most discrepant from the mean. The shape of the z  ~ 2 stellar mass function of passive galaxies is remarkably similar to that at z  ~ 0.9, save for a factor of ~4 lower number density. This similarity suggests that the same mechanism may be responsible for the formation of passive galaxies seen at both these epochs. This same formation mechanism may also operate down to z  ~ 0 if the local PE galaxy mass function, known to be two-component, contains two distinct galaxy populations. This scenario is qualitatively in agreement with recent phenomenological mass-quenching models and extends them to span more than three quarters of the history of the Universe.

Description: Among all known young nearby neutron stars, we search for the neutron star that was born in the same supernova event that formed the Antlia supernova remnant (SNR). We also look for a runaway star that could have been the former companion to the neutron star (if it exists) and then got ejected due to the same supernova. We find the pulsar PSR J0630–2834 to be the best candidate for a common origin with the Antlia SNR. In that scenario, the SNR is 1.2 Myr old and is presently located at a distance of 138 pc. We consider the runaway star HIP 47155 a former companion candidate to PSR J0630–2834. The encounter time and place is consistent with both stars being ejected from the Antlia SNR. We measured the radial velocity of HIP 47155 as 32.42 ± 0.70 km s –1 .

Description: Broad-band coronagraphy with deep nulling and small inner working angle has the potential of delivering images and spectra of exoplanets and other faint objects. In recent years, many coronagraphic schemes have been proposed, the most promising being the optical vortex phase mask coronagraphs. In this paper, a new scheme of broad-band optical scalar vortex coronagraph is proposed and characterized experimentally in the laboratory. Our setup employs a pair of computer-generated phase gratings (one of them containing a singularity) to control the chromatic dispersion of phase plates and achieves a constant peak-to-peak attenuation below 1 10 –3 over a bandwidth of 120 nm centred at 700 nm. An inner working angle of ~/ D is demonstrated along with a raw contrast of 11.5 mag at 2/ D .

Description: A deformation of a neutron star due to its own magnetic field is an important issue in gravitational wave astronomy, since a misaligned rotator with small ellipticity may emit continuous gravitational wave that may be observed by ground-based detectors. Recently, Mastrano et al. evaluated deformations induced by both poloidal and toroidal magnetic field in non-barotropic model stars by neglecting the gravitational field perturbation (Cowling approximation). Following their treatment in non-barotropic fluid and magnetic configurations, we here assess the effect of gravitational perturbation that they neglected. We show that the ellipticity computed with gravitational perturbation is roughly twice as large as that obtained by Cowling approximation. We should allow this amount of error in using the neat analytic treatment proposed by them.

Description: Following the discovery of short-period oscillations in the low-mass pre-white-dwarf component of an eclipsing binary, we have explored the radial (p-mode) stability of extremely low mass stars across a range of composition, effective temperature and luminosity. We have identified the instability boundaries associated with low- to high-order radial oscillations (0 ≤  n  ≤ 13) and show that these are a strong function of both composition and radial order ( n ). The blue edge shifts to higher effective temperature and luminosity with decreasing hydrogen abundance. In addition, high-order modes are more easily excited, and small islands of high-radial-order instability develop, some of which may correspond to real stars. The excitation mechanism is discussed with reference to these instability islands. If the envelope of the low-mass pre-white dwarf 1SWASP J024743.37–251549.2 (J0247–25B) is depleted in hydrogen, it is unstable to high-order p modes. Driving is by the classical mechanism operating in the second helium-ionization zone, with some support from the first helium-ionization zone. The instability is very sensitive to composition, temperature and luminosity. The reported periods, temperature and luminosity of J0247–25B require the envelope hydrogen abundance to lie in the range 0.2 X 0.3, in agreement with current evolution models.

Description: We present an accurate analysis of the H 2 absorption lines from the z abs  ~ 2.4018 damped Lyα system towards HE 0027–1836 observed with the Very Large Telescope Ultraviolet and Visual Echelle Spectrograph (VLT/UVES) as a part of the European Southern Observatory Large Programme ‘The UVES large programme for testing fundamental physics’ to constrain the variation of proton-to-electron mass ratio, μ   m p / m e . We perform cross-correlation analysis between 19 individual exposures taken over three years and the combined spectrum to check the wavelength calibration stability. We notice the presence of a possible wavelength-dependent velocity drift especially in the data taken in 2012. We use available asteroids spectra taken with UVES close to our observations to confirm and quantify this effect. We consider single- and two-component Voigt profiles to model the observed H 2 absorption profiles. We use both linear regression analysis and Voigt profile fitting where μ/μ is explicitly considered as an additional fitting parameter. The two-component model is marginally favoured by the statistical indicators and we get μ/μ = –2.5 ± 8.1 stat  ± 6.2 sys ppm. When we apply the correction to the wavelength-dependent velocity drift, we find μ/μ = –7.6 ± 8.1 stat  ± 6.3 sys ppm. It will be important to check the extent to which the velocity drift we notice in this study is present in UVES data used for previous μ/μ measurements.

Description: Young stellar objects in the inner Galactic region 10° 〈  l  〈 15° and –1° 〈  b  〈 1° were studied using GLIMPSE images and the GLIMPSE data catalogue. A total of 1107 Class I and 1566 Class II sources were identified in this Galactic region. With the help of GLIMPSE 5.8- and 8-μm images, we identified the presence of 10 major star forming sites in the Galactic mid-plane, 8 of which are filamentary while 2 are possible clusters of Class I and II sources. The length of the identified filaments are estimated as 8–33 arcmin (~9–56 pc). The occurrence of a hub–filamentary system is observed in many filamentary star forming sites. Most of the Class I sources are found to be aligned along the length of these filamentary structures, while Class II sources have a random distribution. The mass and age distribution of 425 Class I and 241 Class II sources associated with filaments and clusters were studied through analysis of their spectral energy distribution. Most of the Class I sources detected have mass 〉8 M , while Class II sources have relatively low masses. Class I sources have ages ≤0.5 Myr, while Class II sources have ages in the range ~0.1–3 Myr. By combining our results with information from high mass star forming tracers, we demonstrate that large numbers of high-mass stars are being formed in the 10 regions studied here.

Description: Forthcoming weak lensing shear measurements in surveys such as Large Synoptic Survey Telescope will be sensitive to short-time-scale atmospheric deflections. Orthogonal transfer (OT) imagers reduce the point spread function (PSF) ellipticity and size induced by atmospheric deflections using on-chip electronic tip-tilt corrections, but they also provide a large volume of data on the short-time-scale behaviour of the PSF. We use the OT imager Orthogonal Parallel Transfer Imaging Camera to show that short-time-scale-induced ellipticities obey the t –1/2 time dependence described in Heymans et al. and de Vries et al. even at time-scales shorter than 1 s. We also demonstrate the utility of OT imagers for measuring this relationship on an exposure-by-exposure basis and show evidence for a weak correlation between local windspeed conditions and the rate of decline of atmospheric-induced ellipticity. In addition, we determine that the ellipticity induced by centroid deflections declines more gradually with time than the atmospheric-induced instantaneous ellipticity.

Description: We present a method for populating dark matter simulations with haloes of mass below the resolution limit. It is based on stochastically sampling a field derived from the density field of the halo catalogue, using constraints from the conditional halo mass function n ( m |). We test the accuracy of the method and show its application in the context of building mock galaxy samples. We find that this technique allows precise reproduction of the two-point statistics of galaxies in mock samples constructed with this method. Our results demonstrate that the main information content of a simulation can be communicated efficiently using only a catalogue of the more massive haloes.

Description: We present age distribution matching , a theoretical formalism for predicting how galaxies of luminosity L and colour C occupy dark matter haloes. Our model supposes that there are just two fundamental properties of a halo that determine the colour and brightness of the galaxy it hosts: the maximum circular velocity V max and the redshift z starve that correlates with the epoch at which the star formation in the galaxy ceases. The halo property z starve is intended to encompass physical characteristics of halo mass assembly that may deprive the galaxy of its cold gas supply and, ultimately, quench its star formation. The new, defining feature of the model is that, at fixed luminosity, galaxy colour is in monotonic correspondence with z starve , with the larger values of z starve being assigned redder colours. We populate an N -body simulation with a mock galaxy catalogue based on age distribution matching and show that the resulting mock galaxy distribution accurately describes a variety of galaxy statistics. Our model suggests that halo and galaxy assembly are indeed correlated. We make publicly available our low-redshift, Sloan Digital Sky Survey M r  〈 –19 mock galaxy catalogue, and main progenitor histories of all z  = 0 haloes, at http://logrus.uchicago.edu/~aphearin

Description: The incidence of intranight optical variability (INOV) is known to differ significantly among different classes of powerful active galactic nuclei (AGN). A number of statistical methods have been employed in the literature for testing the presence of INOV in the light curves, sometimes leading to discordant results. In this paper, we compare the INOV characteristics of six prominent classes of AGN, as evaluated using three commonly used statistical tests, namely the 2 -test, the modified C -test and the F -test, which has recently begun to gain popularity. The AGN classes considered are: radio-quiet quasars, radio-intermediate quasars, lobe-dominated quasars, low optical polarization core-dominated quasars, high optical polarization core-dominated quasars and TeV blazars. Our analysis is based on a large body of AGN monitoring data, involving 262 sessions of intranight monitoring of a total 77 AGN, using 1–2 m class optical telescopes located in India. In order to compare the usefulness of the statistical tests, we have also subjected them to a ‘sanity check’ by comparing the number of false positives yielded by each test with the corresponding statistical prediction. The present analysis is intended to serve as a benchmark for future INOV studies of AGN of different classes.

Description: Using spectropolarimetry, we investigate the large-scale magnetic topologies of stars hosting close-in exoplanets. A small survey of 10 stars has been done with the twin instruments Télescope Bernard Lyot /NARVAL and Canada–France–Hawaii Telescope/ESPaDOnS between 2006 and 2011. Each target consists of circular polarization observations covering 7–22 d. For each of the seven targets in which a magnetic field was detected, we reconstructed the magnetic field topology using Zeeman–Doppler imaging. Otherwise, a detection limit has been estimated. Three new epochs of observations of Boo are presented, which confirm magnetic polarity reversal. We estimate that the cycle period is 2 yr, but recall that a shorter period of 240 d cannot still be ruled out. The result of our survey is compared to the global picture of stellar magnetic field properties in the mass–rotation diagram. The comparison shows that these giant planet-host stars tend to have similar magnetic field topologies to stars without detected hot Jupiters. This needs to be confirmed with a larger sample of stars.

Description: We present the first theoretical study of metals in damped-Lyα (DLA) systems at redshift z ~= 7. The features of cold, primordial gas are studied by means of N -body, hydro, chemistry simulations, including atomic and molecular non-equilibrium chemistry, cooling, star formation for Population III and Population II-I regimes, stellar evolution, cosmic metal spreading according to proper yields (for He, C, O, Si, Fe, Mg, S, etc.) and lifetimes and feedback effects. Theoretical expectations are then compared to recently available constraints from DLA observations. We find that DLA galaxies at z ~= 7 account for ~10 per cent of the whole galaxy population and for most of the metal-poor galaxies at these epochs. About 7 per cent of these DLA galaxies contain purely pristine material and ~34 per cent of them consist of very weakly polluted gas, being, therefore, suitable candidates as Population III sites. The remaining ~59 per cent are enriched above ~10 –4 Z . Additionally, DLA candidates appear to have: gas masses 2 x 10 8 M ; very low star formation rate, ~ 10 – 3 – 10 – 2 M yr – 1 (significantly weaker than late-time counterparts); mean molecular fractions covering a fairly wide range, x mol ~ 10 – 3 -10 – 6 ; typical metallicities Z 10 –3 Z and H i column densities $N_{\rm H\,{{\small I}}}\gtrsim 3\times 10^{20}\, {\rm cm}^{-2}$ (in agreement with recent observations). They present no or weak correlations between their gas mass and Z , $N_{\rm H\,{{\small I}}}$ , or x mol ; a moderate correlation between x mol and Z , linked to the ongoing molecular-driven star formation and metal pollution processes; a mild anticorrelation between $N_{\rm H\,{{\small I}}}$ and x mol , due to H depletion into molecules; and a chemical content that is subject to environmental dependences.

Description: We present new Gemini spectroscopical data of the extended emission-line region of the 3C 305 radio galaxy in order to achieve a final answer to the long-standing question about the ionizing mechanism. The spectra show strong kinematic disturbances within the most intense line-emitting region. The relative intensities of the emission lines agree with the hypothesis that the gas is shocked during the interaction of powerful radio jets with the ambient medium. The emission from the recombination region acts as a very effective cooling mechanism, which is supported by the presence of a neutral outflow. However, the observed intensity is almost an order of magnitude lower than expected in a pure shock model. So, autoionizing shock models, in low-density and low-abundance regimes, are required in order to account for the observed emission within the region. This scenario also supports the hypothesis that the optical emitting gas and the X-ray plasma are in pressure balance.

Description: In a recent work (Paper I), we explored the dependence of galaxy stellar population properties derived from broad-band spectral energy distribution fitting on the fitting parameters, e.g. star formation histories (SFHs), age grid, metallicity, initial mass function (IMF), dust reddening and reddening law, filter setup and wavelength coverage. In this paper, we consider the case that also redshift is a free parameter in the fit and study whether one can obtain reasonable estimates of photometric redshifts and stellar population properties at once . As in Paper I, we use mock star-forming as well as passive galaxies placed at various redshifts (0.5–3) as test particles. Mock star-forming galaxies are extracted from a semi-analytical galaxy formation model. We show that for high-redshift star-forming galaxies, photometric redshifts, stellar masses and reddening can be determined simultaneously when using a broad wavelength coverage (including the Lyman and the 4000 Å break) and a wide template setup in the fit. Masses are similarly well recovered (median ~0.2 dex) as at fixed redshift. For old galaxies with little recent star formation (which are at lower redshift in the simulation), masses are better recovered than in the fixed redshift case, such that the median recovered stellar mass improves by up to 0.3 dex (at fixed IMF) whereas the uncertainty in the redshift accuracy increases by only ~0.05. However, a failure in redshift recovery also means a failure in mass recovery. As at fixed redshift, mismatches in SFH and degeneracies between age, dust and now also redshift cause underestimated ages, overestimated reddening and underestimated masses. Stellar masses are best determined at low redshift without reddening in the fit. Masses are then underestimated by only ~0.1 dex whereas redshifts are similarly well recovered. Not surprisingly, the recovery of properties is substantially better for passive galaxies, for which e.g. the mass is recovered only slightly worse than at fixed redshift (underestimated by ~0.02 dex instead of ~0.01, at fixed IMF) using a setup including metallicity effects. In all cases, the recovery of physical parameters is crucially dependent on the wavelength coverage adopted in the fitting because the redshift recovery depends on the wavelength coverage. As is well known, redshifts are best recovered for a wavelength coverage including the Lyman and 4000 Å break. As in Paper I, all effects from changing templates, the wavelength coverage and filters are quantified and scaling relations for the transformation of stellar masses obtained using different fitting parameters, including stellar population models, are provided.

Description: Previous studies of globular cluster (GC) systems show that there appears to be a universal specific GC formation efficiency which relates the total mass of GCs to the virial mass of host dark matter haloes, M vir . In this paper, the specific frequency, S N , and specific GC formation efficiency, , are derived as functions of M vir in Milgromian dynamics, i.e. in modified Newtonian dynamics. In Milgromian dynamics, for the galaxies with GCs, the mass of the GC system, M GC , is a two-component function of M vir instead of a simple linear relation. An observer in a Milgromian universe, who interprets this universe as being Newtonian/Einsteinian, will incorrectly infer a universal constant fraction between the mass of the GC system and a (false) dark matter halo of the baryonic galaxy. In contrast to a universal constant of , in a Milgromian universe, for galaxies with M vir ≤ 10 12 M , decreases with the increase of M vir , while for massive galaxies with M vir 〉 10 12 M , increases with the increase of M vir .

Description: New collisions’ strengths for the mid-infrared (mid-IR) and optical transitions in Ne v are presented. Breit–Pauli-R-Matrix calculations for electron impact excitation are carried out with fully resolved near-threshold resonances at very low energies. In particular, the fine-structure lines at 14 and 24 μm due to transitions among the ground state levels 1s 2 2s 2 2p 3 3 P 0, 1, 2 , and the optical/near-ultraviolet lines at 2973, 3346 and 3426 Å transitions among the 3 P 0, 1, 2 , 1 D 2 , 1 S 0 levels are described. Maxwellian-averaged collision strengths are tabulated for all forbidden transitions within the ground configuration. While some significant differences are found for both the far infrared and the optical transitions compared to previous results, computed line emissivity ratios are in good agreement, but change rapidly in the low temperature range T e  〈 10 000 K. An analysis of the 14/24 μm ratio in low-energy-density (LED) plasma conditions reveals considerable variation; the effective rate coefficient may be dominated by the very low energy behaviour rather than the Maxwellian-averaged collision strengths. Computed values suggest a possible solution to the anomalous mid-IR ratios found to be lower than theoretical limits observed from planetary nebulae and Seyfert galaxies. While such LED conditions may be present in infrared sources, they might be inconsistent with photoionization equilibrium models.

Description: Despite the shallow convective envelopes of Scuti pulsators, solar-like oscillations are theoretically predicted to be excited in those stars as well. To search for such stochastic oscillations, we organized a spectroscopic multisite campaign for the bright, metal-rich Sct star Puppis. We obtained a total of 2763 high-resolution spectra using four telescopes. We discuss the reduction and analysis with the iodine cell technique, developed for searching low-amplitude radial velocity variations, in the presence of high-amplitude variability. Furthermore, we have determined the angular diameter of Puppis to be 1.68 ± 0.03 mas, translating into a radius of 3.52 ± 0.07 R . Using this value, the frequency of maximum power of possible solar-like oscillations is expected at ~43 ± 2 c d –1 (498 ± 23 μHz). The dominant Scuti-type pulsation mode of Puppis is known to be the radial fundamental mode which allows us to determine the mean density of the star, and therefore an expected large frequency separation of 2.73 c d –1 (31.6 μHz). We conclude that (1) the radial velocity amplitudes of the Scuti pulsations are different for different spectral lines; (2) we can exclude solar-like oscillations to be present in Puppis with an amplitude per radial mode larger than 0.5 m s –1 .

Description: We present an analytic model for bolometric light curves which are powered by the interaction between supernova ejecta and a dense circumstellar medium. This model is aimed at modelling Type IIn supernovae to determine the properties of their supernova ejecta and circumstellar medium. Our model is not restricted to the case of steady mass loss and can be applied broadly. We only consider the case in which the optical depth of the unshocked circumstellar medium is not high enough to affect the light curves. We derive the luminosity evolution based on an analytic solution for the evolution of a dense shell created by the interaction. We compare our model bolometric light curves to observed bolometric light curves of three Type IIn supernovae (2005ip, 2006jd, 2010jl) and show that our model can constrain their supernova ejecta and circumstellar medium properties. Our analytic model is supported by numerical light curves from the same initial conditions.

Description: The ever increasing size and complexity of data coming from simulations of cosmic structure formation demand equally sophisticated tools for their analysis. During the past decade, the art of object finding in these simulations has hence developed into an important discipline itself. A multitude of codes based upon a huge variety of methods and techniques have been spawned yet the question remained as to whether or not they will provide the same (physical) information about the structures of interest. Here we summarize and extent previous work of the ‘halo finder comparison project’: we investigate in detail the (possible) origin of any deviations across finders. To this extent, we decipher and discuss differences in halo-finding methods, clearly separating them from the disparity in definitions of halo properties. We observe that different codes not only find different numbers of objects leading to a scatter of up to 20 per cent in the halo mass and V max function, but also that the particulars of those objects that are identified by all finders differ. The strength of the variation, however, depends on the property studied, e.g. the scatter in position, bulk velocity, mass and the peak value of the rotation curve is practically below a few per cent, whereas derived quantities such as spin and shape show larger deviations. Our study indicates that the prime contribution to differences in halo properties across codes stems from the distinct particle collection methods and – to a minor extent – the particular aspects of how the procedure for removing unbound particles is implemented. We close with a discussion of the relevance and implications of the scatter across different codes for other fields such as semi-analytical galaxy formation models, gravitational lensing and observables in general.

Description: The well-established Type Ia remnant of Tycho's supernova (SN 1572) reveals discrepant ambient medium-density estimates based on either the measured dynamics or the X-ray emission properties. This discrepancy can potentially be solved by assuming that the supernova remnant (SNR) shock initially moved through a stellar wind bubble, but is currently evolving in the uniform interstellar medium with a relatively low density. We investigate this scenario by combining hydrodynamical simulations of the wind-loss phase and the SNR evolution with a coupled X-ray emission model, which includes non-equilibrium ionization. For the explosion models we use the well-known W7 deflagration model and the delayed detonation model that was previously shown to provide good fits to the X-ray emission of Tycho's SNR. Our simulations confirm that a uniform ambient density cannot simultaneously reproduce the dynamical and X-ray emission properties of Tycho. In contrast, models that considered that the remnant was evolving in a dense, but small, wind bubble reproduce reasonably well both the measured X-ray emission spectrum and the expansion parameter of Tycho's SNR. Finally, we discuss possible mass-loss scenarios in the context of single- and double-degenerate models which possibly could form such a small dense wind bubble.

Description: We present a numerical study of the evolution of molecular clouds, from their formation by converging flows in the warm interstellar medium, to their destruction by the ionizing feedback of the massive stars they form. We improve with respect to our previous simulations by including a different stellar-particle formation algorithm, which allows them to have masses corresponding to single stars rather than to small clusters, and with a mass distribution following a near-Salpeter stellar initial mass function. We also employ a simplified radiative-transfer algorithm that allows the stellar particles to feedback on the medium at a rate that depends on their mass and the local density. Our results are as follows: (a) contrary to the results from our previous study, where all stellar particles injected energy at a rate corresponding to a star of ~10 M , the dense gas is now completely evacuated from 10 pc regions around the stars within 10–20 Myr, suggesting that this feat is accomplished essentially by the most massive stars. (b) At the scale of the whole numerical simulations, the dense gas mass is reduced by up to an order of magnitude, although star formation (SF) never shuts off completely, indicating that the feedback terminates SF locally, but new SF events continue to occur elsewhere in the clouds. (c) The SF efficiency (SFE) is maintained globally at the ~10 per cent level, although locally, the cloud with largest degree of focusing of its accretion flow reaches SFE ~30 per cent. (d) The virial parameter of the clouds approaches unity before the stellar feedback begins to dominate the dynamics, becoming much larger once feedback dominates, suggesting that clouds become unbound as a consequence of the stellar feedback, rather than unboundness being the cause of a low SFE. (e) The erosion of the filaments that feed the star-forming clumps produces chains of isolated dense blobs reminiscent of those observed in the vicinity of the dark globule B68.

Description: We present a detailed analysis of absorption systems along the line of sight towards QSO PKS 0237–233 using a high-resolution spectrum of signal-to-noise ratio ~60–80 obtained with the Ultraviolet and Visual Echelle Spectrograph mounted on the Very Large Telescope (VLT/UVES). This line of sight is known to show a remarkable overdensity of C iv systems that has been interpreted as revealing the presence of a supercluster of galaxies. A detailed analysis of each of these absorption systems is presented. In particular, for the z abs  = 1.6359 (with two components of log N H I [cm –2 ] = 18.45, 19.05) and z abs  = 1.6720 (log N H I  = 19.78) sub-damped Lyα systems (sub-DLAs), we measure accurate abundances (resp. [O/H] = –1.63 ± 0.07 and [Zn/H] = –0.57 ± 0.05 relative to solar). While the depletion of refractory elements on to dust grains in both sub-DLAs is not noteworthy, photoionization models show that ionization effects are important in a part of the absorbing gas of the sub-DLA at z abs  = 1.6359 (H i is 95 per cent ionized) and in a part of the gas of the sub-DLA at z abs  = 1.6720. The C iv clustering properties along the line of sight is studied in order to investigate the nature of the observed overdensity. We conclude that despite the unusually high number of C iv systems detected along the line of sight, there is no compelling evidence for the presence of a single unusual overdensity and that the situation is consistent with chance coincidence.

Description: We present a statistically optimal and model-independent method to extract the pressure profile of hot gas in the intracluster medium (ICM). Using the thermal Sunyaev–Zeldovich effect, we constrain the mean pressure profile of the ICM by appropriately considering all primary cosmic microwave background (CMB) and instrumental noise correlations, while using the maximum resolution and sensitivity of all frequency channels. As a first application, we analyse CMB maps of Wilkinson Microwave Anisotropy Probe 9-year data through a study of the Meta-Catalogue of X-ray Detected Clusters of Galaxies. We constrain the universal pressure profile out to 4 R 500 with 15 confidence, though our measurements are only significant out to R 200 . Using a temperature profile constrained from X-ray observations, we measure the mean gas mass fraction out to R 200 . Within statistical and systematic uncertainties, our constraints are compatible with the cosmic baryon fraction and the expected gas fraction in haloes. While Planck multifrequency CMB data are expected to reduce statistical uncertainties by a factor of ~20, we argue that systematic errors in determining mass of clusters dominate the uncertainty in gas mass fraction measurements at the level of ~20 per cent.

Description: In the present work we report theoretical Stark widths and shifts calculated using the Griem semi-empirical approach, corresponding to 237 spectral lines of Mg iii . Data are presented for an electron density of 10 17 cm –3 and temperatures T  = 0.5–10.0 (10 4 K). The matrix elements used in these calculations have been determined from 23 configurations of Mg iii : 2s 2 2p 6 , 2s 2 2p 5 3p, 2s 2 2p 5 4p, 2s 2 2p 5 4f and 2s 2 2p 5 5f for even parity and 2s 2 2p 5 n s ( n  = 3–6), 2s 2 2p 5 n d ( n  = 3–9), 2s 2 2p 5 5g and 2s2p 6 n p ( n  = 3–8) for odd parity. For the intermediate coupling (IC) calculations, we use the standard method of least-squares fitting from experimental energy levels by means of the Cowan computer code. Also, in order to test the matrix elements used in our calculations, we present calculated values of 70 transition probabilities of Mg iii spectral lines and 14 calculated values of radiative lifetimes of Mg iii levels. There is good agreement between our calculations and experimental radiative lifetimes. Spectral lines of Mg iii are relevant in astrophysics and also play an important role in the spectral analysis of laboratory plasma. Theoretical trends of the Stark broadening parameter versus the temperature for relevant lines are presented. No values of Stark parameters can be found in the bibliography.

Description: We present chemical abundance measurements from high-resolution observations of five sub-damped Lyman α absorbers (sub-DLAs) at 1.7 〈  z  〈 2.4 observed with the Magellan Inamori Kyocera Echelle (MIKE) spectrograph on the 6.5-m Magellan II (Clay) telescope. Lines of Zn ii , Mg i , Mg ii , Al ii , Al iii , S ii , Si ii , Si iv , C ii , C ii *, C iv , Ni ii , Mn ii and Fe ii were detected and column densities were determined. The metallicity of the absorbing gas, inferred from the nearly undepleted element Zn, is in the range of 〈–0.95 to +0.25 dex for the five absorbers in our sample, with three of the systems being near-solar or supersolar. We also investigate the effect of ionization on the observed abundances using photoionization modelling. Combining our data with other sub-DLA and DLA data from the literature, we report the most complete existing determination of the metallicity versus redshift relation for sub-DLAs and DLAs. We confirm the suggestion from previous investigations that sub-DLAs are, on average, more metal rich than DLAs and may evolve faster. We also discuss relative abundances and abundance ratios in these absorbers. The more metal-rich systems show significant dust depletion levels, as suggested by the ratios [Zn/Cr] and [Zn/Fe]. For the majority of the systems in our sample, the [Mn/Fe] versus [Zn/H] trend is consistent with that seen previously for lower redshift sub-DLAs. We also measure the velocity width values for the sub-DLAs in our sample from unsaturated absorption lines of Fe ii 2344, 2374, 2600 Å, and examine where these systems lie in a plot of metallicity versus velocity dispersion. Finally, we examine cooling rate versus H i column density in these sub-DLAs, and compare this with the data from DLAs and the Milky Way interstellar medium. We find that most of the systems in our sample show higher cooling rate values compared to those seen in the DLAs.

Description: Rate coefficients for spontaneous and stimulated radiative association of the He $_{2}^{+}$ molecular ion on the spin-quartet manifold are presented as functions of temperature considering the association with rotational-vibrational states of the lowest quartet electronic states $b^{4}\Sigma ^{+}_{u}$ and $c^{4}\Sigma ^{+}_{g}$ from the continuum states of the low-lying excited quartet states. The rate coefficients are obtained from the cross sections for radiative association, which are calculated by solving the Schrödinger equations for bound and continuum states supported by the corresponding Born–Oppenheimer potential energy curves. The rate coefficients for radiative association to the b state are several orders of magnitude larger than for radiative association to the c state. For all considered temperatures the spontaneous $1^{4}\Pi _{g} \rightarrow b^{4}\Sigma ^{+}_{u}$ process is dominant. Stimulation of the radiative association by blackbody radiation has a significant influence only on the $c^{4}\Sigma ^{+}_{g} \rightarrow b^{4}\Sigma ^{+}_{u}$ process at temperatures below 1000 K.

Description: The Uranian satellite Miranda presents a high inclination (4 $_{.}^{\circ}$ 338) and evidence of resurfacing. For the past 20 years it has been accepted that this inclination is due to the past trapping into the 3:1 resonance with Umbriel. These last years there is a renewal of interest for the Uranian system since the Hubble Space Telescope permitted the detection of an inner system of rings and small embedded satellites, their dynamics being of course ruled by the main satellites. For this reason, we here propose to revisit the long-term dynamics of Miranda, using modern tools like intensive computing facilities and new chaos indicators [Mean Exponential Growth factor of Nearby Orbits (MEGNO) and frequency map analysis]. As in the previous studies, we find the resonance responsible for the inclination of Miranda and the secondary resonances associated, likely to have stopped the rise of Miranda's inclination at 4 $_{.}^{\circ}$ 5, identify with the frequency analysis tool the libration arguments of the secondary resonances involved, and show in particular that capture into a 3:1 secondary resonance and subsequent capture into a 2:1 secondary resonance may have disrupted the primary resonance with an inclination of Miranda of 4 $_{.}^{\circ}$ 395.

Description: Certain carbon-enhanced metal-poor stars likely obtained their composition via pollution from some of the earliest generations of asymptotic giant branch stars and as such provide important clues to early Universe nucleosynthesis. Recently, Kinman et al. discovered that the highly carbon- and barium-enriched metal-poor star SDSS J1707+58 is in fact an RR Lyrae pulsator. This gives us an object in a definite evolutionary state where the effects of dilution of material during the main sequence are minimized owing to the object having passed through first dredge-up. We perform detailed stellar modelling of putative progenitor systems in which we accreted material from asymptotic giant branch stars in the mass range 1–2 M . We investigate how the surface abundances are affected by the inclusion of mechanisms like thermohaline mixing and gravitational settling. While we are able to find a reasonable fit to the carbon and sodium abundances of SDSS J1707+58, suggesting accretion of around 0.1 M from a 2 M companion, the strontium and barium abundances remain problematic and this object may have experienced something other than a standard s -process. We have more success in fitting the abundances of the mildly carbon-enriched, metal-poor RR Lyrae pulsator TY Gru (CS 22881–071), which we suggest received 0.1 M of material from a companion of around 1 M .

Description: Infrared shells and bubbles are ubiquitous in the Galaxy and can generally be associated with H ii regions formed around young, massive stars. In this paper, we use high-resolution 3D SPH simulations to explore the effect of a single O7 star emitting photons at 10 49 s –1 and located at the centre of a molecular cloud with mass 10 4 M and radius 6.4 pc; the internal structure of the cloud is characterized by its fractal dimension, ${\cal D}$ (with $2.0\le {\cal D}\le 2.8$ ), and the variance of its (lognormal) density distribution, $\sigma _{{\rm O}}^2$ (with $0.36 \le \sigma _{{\rm O}}^2 \le 1.42$ ). Our study focuses on the morphology of the swept-up cold gas and the distribution and statistics of the resulting star formation. If the fractal dimension is low, the border of the H ii region is dominated by extended shell-like structures, and these break up into a small number of massive high-density clumps which then spawn star clusters; star formation occurs relatively quickly, and delivers somewhat higher stellar masses. Conversely, if the fractal dimension is high, the border of the H ii region is dominated by a large number of pillars and cometary globules, which contain compact dense clumps and tend to spawn single stars or individual multiple systems; star formation occurs later, the stellar masses are somewhat lower, and the stars are more widely distributed.

Description: Multi-object adaptive optics (MOAO) has been demonstrated by the CANARY instrument on the William Herschel Telescope. However, for proposed MOAO systems on the next-generation extremely large telescopes (ELTs), such as ELT Adaptive optics for GaLaxy Evolution (EAGLE), many challenges remain. Here we investigate requirements that MOAO operation places on deformable mirrors (DMs) using a full end-to-end Monte Carlo adaptive optics (AO) simulation code. By taking into consideration a prior global ground-layer (GL) correction, we show that actuator density for the MOAO DMs can be reduced with little performance loss. We note that this reduction is only possible with the addition of a GL DM, whose order is greater than or equal to that of the original MOAO mirrors. The addition of a GL DM of lesser order does not affect system performance (if tip/tilt star sharpening is ignored). We also quantify the maximum mechanical DM stroke requirements (3.5 μm desired) and provide tolerances for the DM alignment accuracy, both lateral (to within an eighth of a sub-aperture) and rotational (to within 0 $_{.}^{\circ}$ 2). By presenting results over a range of laser guide star asterism diameters, we ensure that these results are equally applicable for laser tomographic AO systems. We provide the opportunity for significant cost savings to be made in the implementation of MOAO systems, resulting from the lower requirement for DM actuator density.

Description: We study the formation and evolution of brightest cluster galaxies starting from a z  = 2 population of quiescent ellipticals and following them to z  = 0. To this end, we use a suite of nine high-resolution dark matter only simulations of galaxy clusters in a cold dark matter (CDM) universe. We develop a scheme in which simulation particles are weighted to generate realistic and dynamically stable stellar density profiles at z  = 2. Our initial conditions assign a stellar mass to every identified dark halo as expected from abundance matching; assuming that there exists a one-to-one relation between the visible properties of galaxies and their host haloes. We set the sizes of the luminous components according to the observed relations for z  ~ 2 massive quiescent galaxies. We study the evolution of the mass–size relation, the fate of satellite galaxies and the mass aggregation of the cluster central. From z  = 2, these galaxies grow on average in size by a factor of 5 to 10 and in galaxy mass by 2 to 3. The stellar mass of our simulated BCGs grow by a factor of ~2.1 in the range 0.3 〈 z  〈 1.0, consistent with observations, and by a factor of ~1.4 in the range 0.0 〈 z  〈 0.3. Furthermore, the non-central galaxies evolve on to the present-day mass–size relation by z  = 0. Assuming passively evolving stellar populations, we present surface brightness profiles for our cluster centrals which resemble those observed for the cDs in similar mass clusters both at z  = 0 and at z  = 1. This demonstrates that the CDM cosmology does indeed predict minor and major mergers to occur in galaxy clusters with the frequency and mass ratio distribution required to explain the observed growth in size of passive galaxies since z  = 2. Our experiment shows that brightest cluster galaxies could, in principle, form through dissipationless mergers of quiescent massive z  = 2 galaxies, without substantial additional star formation.

Description: We construct simple triaxial generalizations of Navarro–Frenk–White haloes. The models have elementary gravitational potentials, together with a density that is cusped like 1/ r at small radii and falls off like 1/ r 3 at large radii. The ellipticity varies with radius in a manner that can be tailored to the user's specification. The closed periodic orbits in the planes perpendicular to the short and long axes of the model are well described by epicyclic theory, and can be used as building blocks for long-lived discs. As an application, we carry out the simulations of thin discs of satellites in triaxial dark halo potentials. This is motivated by the recent claims of an extended, thin disc of satellites around the M31 galaxy with a vertical rms scatter of ~12 kpc and a radial extent of ~300 kpc. We show that a thin satellite disc can persist over cosmological times if and only if it lies in the planes perpendicular to the long or short axis of a triaxial halo, or in the equatorial or polar planes of a spheroidal halo. In any other orientation, then the disc thickness doubles on ~5 Gyr time-scales and so must have been born with an implausibly small vertical scaleheight.

Description: We describe simple useful toy models for key processes of galaxy formation in its most active phase, at z  〉 1, and test the approximate expressions against the typical behaviour in a suite of high-resolution hydro-cosmological simulations of massive galaxies at z=4–1 . We address in particular the evolution of (a) the total mass inflow rate from the cosmic web into galactic haloes based on the EPS approximation, (b) the penetration of baryonic streams into the inner galaxy, (c) the disc size, (d) the implied steady-state gas content and star formation rate (SFR) in the galaxy subject to mass conservation and a universal star formation law, (e) the inflow rate within the disc to a central bulge and black hole as derived using energy conservation and self-regulated Q  ~ 1 violent disc instability (VDI) and (f) the implied steady state in the disc and bulge. The toy models provide useful approximations for the behaviour of the simulated galaxies. We find that (a) the inflow rate is proportional to mass and to (1 +  z ) 5/2 , (b) the penetration to the inner halo is ~50 per cent at z=4–2 , (c) the disc radius is ~5 per cent of the virial radius, (d) the galaxies reach a steady state with the SFR following the accretion rate into the galaxy, (e) there is an intense gas inflow through the disc, comparable to the SFR, following the predictions of VDI and (f) the galaxies approach a steady state with the bulge mass comparable to the disc mass, where the draining of gas by SFR, outflows and disc inflows is replenished by fresh accretion. Given the agreement with simulations, these toy models are useful for understanding the complex phenomena in simple terms and for back-of-the-envelope predictions.

Description: New detections of debris discs at submillimetre wavelengths present highly valuable complementary information to prior observations of these sources at shorter wavelengths. Characterization of discs through spectral energy distribution modelling including the submillimetre fluxes is essential for our basic understanding of disc mass and temperature, and presents a starting point for further studies using millimetre interferometric observations. In the framework of the ongoing SCUBA-2 Observations of Nearby Stars, the instrument SCUBA-2 on the James Clerk Maxwell Telescope was used to provide measurements of 450 and 850 μm fluxes towards a large sample of nearby main-sequence stars with debris discs detected previously at shorter wavelengths. We present the first results from the ongoing survey, concerning 850 μm detections and 450 μm upper limits towards 10 stars, the majority of which are detected at submillimetre wavelengths for the first time. One, or possibly two, of these new detections is likely a background source. We fit the spectral energy distributions of the star+disc systems with a blackbody emission approach and derive characteristic disc temperatures. We use these temperatures to convert the observed fluxes to disc masses. We obtain a range of disc masses from 0.001 to 0.1 M , values similar to the prior dust mass measurements towards debris discs. There is no evidence for evolution in dust mass with age on the main sequence, and indeed the upper envelope remains relatively flat at 0.5 M at all ages. The inferred disc masses are lower than those from disc detections around pre-main-sequence stars, which may indicate a depletion of solid mass. This may also be due to a change in disc opacity, though limited sensitivity means that it is not yet known what fraction of pre-main-sequence stars have discs with dust masses similar to debris disc levels. New, high-sensitivity detections are a path towards investigating the trends in dust mass evolution.

Description: Accretion of matter on to the surface of a freely precessing neutron star (NS) with a complex non-dipole magnetic field can explain the change of X-ray pulse profiles of Her X-1 observed by RXTE with the phase of the 35-d cycle. We demonstrate this using all available measurements of X-ray pulse profiles in the 9–13 keV energy range obtained with the RXTE /Proportional Counter Array (PCA). The measured profiles guided the elaboration of a geometrical model and the definition of locations of emitting poles, arcs and spots on the NS surface which satisfactorily reproduce the observed pulse profiles and their dependence on free precession phase. We have found that the observed trend of the times of the 35-d turn-ons on the O–C diagram, which can be approximated by a collection of consecutive linear segments around the mean value, can be described by our model by assuming a variable free precession period, with a fractional period change of about a few per cent. Under this assumption and using our model, we have found that the times of phase zero of the NS free precession (which we identify with the maximum separation of the brightest spot on the NS surface with the NS spin axis) occur about 1.6 d after the mean turn-on times inside each ‘stable’ epoch, producing a linear trend on the O–C diagram with the same slope as the observed times of turn-ons. We propose that the 2.5 per cent changes in the free precession period that occur on time scales of several to tens of 35-d cycles can be related to wandering of the principal inertia axis of the NS body due to variations in the patterns of accretion on to the NS surface. The closeness of periods of the disc precession and the NS free precession can be explained by the presence of a synchronization mechanism in the system, which modulates the dynamical interaction of the gas streams and the accretion disc with the NS free precession period.

Description: The trigonometric parallaxes of 71 stars with large proper motion were determined with the 26-inch refractor at Pulkovo Observatory. Relative parallaxes of the targets were derived using three or four separate series of observations (three or four pointings over 1.5 or 2 years for each one). Observations were performed over the period 2007–2011. We used from 5 to 20 reference stars per field. We applied a correction from relative to absolute parallax based on the photometric parallaxes of reference stars. The latter were estimated from infrared colours ( J  –  Ks ) and the reduced proper motions of reference stars, and from simulated colour–magnitude diagrams. The trigonometric parallaxes of 30 stars out of our 71 targets were previously unknown. In most cases, typical standard errors were 2 to 6 mas. The General Catalogue of Trigonometric Stellar Parallaxes contains data for 41 stars of our 71 targets. On the whole, Pulkovo parallaxes are in a good agreement with Yale results. The values of parallax differences are within –5 mas to +5 mas in 25 of the 41 stars. Considerable discrepancies are revealed in several cases. They may be explained by the presence of systematic errors in the data of both projects or by possible orbital motions not taken account for the case of double stars. The targets are mostly main sequence M-dwarfs closer than 50 pc. Three stars are white dwarfs and five stars are halo subdwarfs.

Description: Wojtak et al. have stacked 7800 clusters from the Sloan Digital Sky Survey (SDSS) in redshift space. They find a small net blueshift for the cluster galaxies relative to the brightest cluster galaxies, which agrees quite well with the gravitational redshift predicted from general relativity. Zhao et al. have pointed out that, in addition to the gravitational redshift, one would expect to see transverse Doppler (TD) redshifts, so 〈 z 〉 = –〈〉 + 〈β 2 〉/2 with β the 3D source velocity in units of c , and that these two effects are generally of the same order. Here, we show that there are other corrections that are also of the same order of magnitude. The fact that we observe galaxies on our past light cone results in a bias such that more of the galaxies observed are moving away from us in the frame of the cluster than are moving towards us. This causes the observed average redshift to be $\langle \delta z \rangle = -\langle \Phi \rangle + \langle \beta ^2 \rangle / 2 + \langle \beta _x^2 \rangle$ , with β x the line-of-sight velocity. That is if we average over galaxies with equal weight. If the galaxies in each cluster are weighted by their fluence, or equivalently if we do not resolve the moving sources, and make an average of the mean redshift giving equal weight per photon, the observed redshift is 〈 z 〉 = –〈〉 – 〈β 2 〉/2, so the kinematical effect is then opposite to the usual transverse Doppler effect. In the Wojtak, Hansen & Hjorth experiment, the weighting is a step-function because of the flux limit for inclusion in the spectroscopic sample and the result is different again, and depends on the details of the luminosity function and the spectral energy distributions of the galaxies. Including these effects substantially modifies the blueshift profile. We show that in-fall and out-flow have very small effect over the relevant range of impact parameters but out-flow becomes significant and needs to be taken into account for measurements on larger scales.

Description: We have performed N -body simulations of globular clusters (GCs) in order to estimate a detection rate of mergers of binary stellar mass black holes (BBHs) by means of gravitational wave (GW) observatories. For our estimate, we have only considered mergers of BBHs which escape from GCs (BBH escapers). BBH escapers merge more quickly than BBHs inside GCs because of their small semimajor axes. N -body simulation cannot deal with a GC with the number of stars N  ~ 10 6 due to its high calculation cost. We have simulated dynamical evolution of small N clusters (10 4 N 10 5 ), and have extrapolated our simulation results to large N clusters. From our simulation results, we have found the following dependence of BBH properties on N . BBHs escape from a cluster at each two-body relaxation time at a rate proportional to N . Semimajor axes of BBH escapers are inversely proportional to N , if initial mass densities of clusters are fixed. Eccentricities, primary masses and mass ratios of BBH escapers are independent of N . Using this dependence of BBH properties, we have artificially generated a population of BBH escapers from a GC with N  ~ 10 6 , and have estimated a detection rate of mergers of BBH escapers by next-generation GW observatories. We have assumed that all the GCs are formed 10 or 12 Gyr ago with their initial numbers of stars N i  = 5 10 5 –2 10 6 and their initial stellar mass densities inside their half-mass radii h,i  = 6 10 3 –10 6 M pc –3 . Then, the detection rate of BBH escapers is 0.5–20 yr –1 for a BH retention fraction R BH  = 0.5. A few BBH escapers are components of hierarchical triple systems, although we do not consider secular perturbation on such BBH escapers for our estimate. Our simulations have shown that BHs are still inside some of GCs at the present day. These BHs may marginally contribute to BBH detection.

Description: In the past decade many kinematic groups of young stars (〈100 Myr) were discovered in the solar neighbourhood. Since the most interesting period of planet formation overlaps with the age of these groups, their well dated members are attractive targets for exoplanet searches by direct imaging. We combined astrometric, photometric and X-ray data, and applied strict selection criteria to explore the stellar content of five nearby moving groups. We identified more than 100 potential new candidate members in the β Pic moving group, and in the Tucana-Horologium, Columba, Carina and Argus associations. In order to further assess and confirm their membership status, we analysed radial velocity data and lithium equivalent widths extracted from high-resolution spectra of 54 candidate stars. We identified 35 new probable/possible young moving group members: four in the β Pic moving group, 11 in the Columba association, 16 in the Carina association and four in the Argus association. We found serendipitously a new AB Dor moving group member as well. For four Columba systems Hipparcos -based parallaxes have already been available and as they are consistent with the predicted kinematic parallaxes, they can be considered as secure new members.

Description: The application to observational data of the generalized scaling relations (gSRs) presented in Ettori et al. 2012 is here discussed. We extend further the formalism of the gSR in the self-similar model for X-ray galaxy clusters, showing that for a generic relation $M_{\rm tot} \propto L^{\alpha } M_{\rm g}^{\beta } T^{\gamma }$ , where L , M g and T are the gas luminosity, mass and temperature, respectively, the values of the slopes lay in the plane 4α + 3β + 2 = 3. Using published data set, we show that some projections of the gSR are the most efficient relations, holding among observed physical quantities in the X-ray band, to recover the cluster gravitating mass. This conclusion is based on the evidence that they provide the lowest 2 , the lowest total scatter and the lowest intrinsic scatter among the studied scaling laws on both galaxy group and cluster mass scales. By the application of the gSR, the intrinsic scatter is reduced in all the cases down to a relative error on the reconstructed mass below 16 per cent. The best-fitting relations are $M_{\rm tot} \propto M_{\rm g}^a T^{1.5-1.5 a}$ , with a 0.4, and M tot    L a T 1.5 – 2 a , with a 0.15. As by-product of this study, we provide the estimates of the gravitating mass at  = 500 for 120 objects (50 from the Mahdavi et al. sample, 16 from Maughan sample; 31 from Pratt et al. sample; 23 from Sun et al. sample), 114 of which are unique entries. The typical relative error on the mass provided from the gSR only (i.e. not propagating any uncertainty associated with the observed quantities) ranges between 3 and 5 per cent on cluster scale and is about 10 per cent for galaxy groups. With respect to the hydrostatic values used to calibrate the gSR, the masses are recovered with deviations of the order of 10 per cent due to the different mix of relaxed/disturbed objects present in the considered samples. In the extreme case of a gSR calibrated with relaxed systems, the hydrostatic mass in disturbed objects is overestimated by about 20 per cent.

Description: We present an analysis of the X-ray time lags for the highly variable Seyfert 1 galaxy NGC 4051, based on a series of XMM–Newton observations taken in 2009. We investigate the Fourier frequency dependent time lags in the light curves between the 0.3–1.0 keV and 2.0–5.0 keV energy bands as a function of source flux, including simultaneous modelling of the resulting lag-frequency spectra. We find the shape of the lag-frequency spectra to vary significantly and systematically with source flux. We model the lag-frequency spectra using simple transfer functions, and find that two time lag components are required, one in each energy band. The simplest acceptable fits have only the relative contribution of the lagged component in the hard band varying with flux level, which can be associated with changes in the energy spectrum. We discuss the interpretation of these results in terms of the currently popular models for X-ray time lags.