ALBERT

Description: We investigate the impact of the new LUNA rate for the nuclear reaction 22 Ne( p , ) 23 Na on the chemical ejecta of intermediate-mass stars, with particular focus on the thermally pulsing asymptotic giant branch (TP-AGB) stars that experience hot-bottom burning. To this aim, we use the PARSEC and COLIBRI codes to compute the complete evolution, from the pre-main sequence up to the termination of the TP-AGB phase, of a set of stellar models with initial masses in the range 3.0–6.0 M and metallicities Z i = 0.0005, 0.006 and 0.014. We find that the new LUNA measures have much reduced the nuclear uncertainties of the 22 Ne and 23 Na AGB ejecta that drop from factors of ~=10 to only a factor of few for the lowest metallicity models. Relying on the most recent estimations for the destruction rate of 23 Na, the uncertainties that still affect the 22 Ne and 23 Na AGB ejecta are mainly dominated by the evolutionary aspects (efficiency of mass-loss, third dredge-up, convection). Finally, we discuss how the LUNA results impact on the hypothesis that invokes massive AGB stars as the main agents of the observed O–Na anticorrelation in Galactic globular clusters. We derive quantitative indications on the efficiencies of key physical processes (mass-loss, third dredge-up, sodium destruction) in order to simultaneously reproduce both the Na-rich, O-poor extreme of the anticorrelation and the observational constraints on the CNO abundance. Results for the corresponding chemical ejecta are made publicly available.

Description: We fitted the 3–180 keV spectrum of all the observations of the neutron star low-mass X-ray binary 4U 1636–53 taken with the Rossi X-ray Timing Explorer using a model that includes a thermal Comptonization component. We found that in the low hard state the power-law index of this component, , gradually increases as the source moves in the colour–colour diagram. When the source undergoes a transition from the hard to the soft state drops abruptly; once the source is in the soft state increases again and then decreases gradually as the source spectrum softens further. The changes in , together with changes of the electron temperature, reflect changes of the optical depth in the corona. The lower kilohertz quasi-periodic oscillation (kHz QPO) in this source appears only in observations during the transition from the hard to the soft state, when the optical depth of the corona is high and changes depends strongly upon the position of the source in the colour–colour diagram. Our results are consistent with a scenario in which the lower kHz QPO reflects a global mode in the system that results from the resonance between the disc and/or the neutron star surface, and the Comptonizing corona.

Description: Supermassive stars (SMSs; ~10 5 M ) formed from metal-free gas in the early Universe attract attention as progenitors of supermassive black holes observed at high redshifts. To form SMSs by accretion, central protostars must accrete at as high rates as ~0.1–1 M yr –1 . Such protostars have very extended structures with bloated envelopes, like supergiant stars, and are called supergiant protostars (SGPSs). Under the assumption of hydrostatic equilibrium, SGPSs have density-inverted layers, where the luminosity becomes locally super-Eddington, near the surface. If the envelope matter is allowed to flow out, however, a stellar wind could be launched and hinder the accretion growth of SGPSs before reaching the supermassive regime. We examine whether radiation-driven winds are launched from SGPSs by constructing steady and spherically symmetric wind solutions. We find that the wind velocity does not reach the escape velocity in any case considered. This is because once the temperature falls below ~10 4 K, the opacity plummet drastically owing to the recombination of hydrogen and the acceleration ceases suddenly. This indicates that, in realistic non-steady cases, even if outflows are launched from the surface of SGPSs, they would fall back again. Such a ‘wind’ does not result in net mass-loss and does not prevent the growth of SGPSs. In conclusion, SGPSs will grow to SMSs and eventually collapse to massive black holes of ~10 5 M , as long as the rapid accretion is maintained.

Description: The emergence of cosmic structure is commonly considered one of the most complex phenomena in nature. However, this complexity has never been defined nor measured in a quantitative and objective way. In this work, we propose a method to measure the information content of cosmic structure and to quantify the complexity that emerges from it, based on Information Theory. The emergence of complex evolutionary patterns is studied with a statistical symbolic analysis of the datastream produced by state-of-the-art cosmological simulations of forming galaxy clusters. This powerful approach allows us to measure how many bits of information is necessary to predict the evolution of energy fields in a statistical way, and it offers a simple way to quantify when, where and how the cosmic gas behaves in complex ways. The most complex behaviours are found in the peripheral regions of galaxy clusters, where supersonic flows drive shocks and large energy fluctuations over a few tens of million years. Describing the evolution of magnetic energy requires at least twice as large amount of bits as required for the other energy fields. When radiative cooling and feedback from galaxy formation are considered, the cosmic gas is overall found to double its degree of complexity. In the future, Cosmic Information Theory can significantly increase our understanding of the emergence of cosmic structure as it represents an innovative framework to design and analyse complex simulations of the Universe in a simple, yet powerful way.

Description: We present the results of two-dimensional hydrodynamic simulations of self-gravitating circumbinary discs around binaries whose parameters match those of the circumbinary planet-hosting systems Kepler-16, Kepler-34 and Kepler-35. Previous work has shown that non-self-gravitating discs in these systems form an eccentric precessing inner cavity due to tidal truncation by the binary, and planets which form at large radii migrate until stalling at this cavity. Whilst this scenario appears to provide a natural explanation for the observed orbital locations of the circumbinary planets, previous simulations have failed to match the observed planet orbital parameters. The aim of this work is to examine the role of self-gravity in modifying circumbinary disc structure as a function of disc mass, prior to considering the evolution of embedded circumbinary planets. In agreement with previous work, we find that for disc masses between one and five times the minimum mass solar nebula (MMSN), disc self-gravity affects modest changes in the structure and evolution of circumbinary discs. Increasing the disc mass to 10 or 20 MMSN leads to two dramatic changes in disc structure. First, the scale of the inner cavity shrinks substantially, bringing its outer edge closer to the binary. Secondly, in addition to the eccentric inner cavity, additional precessing eccentric ring-like features develop in the outer regions of the discs. If planet formation starts early in the disc lifetime, these changes will have a significant impact on the formation and evolution of planets and precursor material.

Description: In this paper, we present a multiwavelength investigation of the star-forming complex IRAS 20286+4105, located in the Cygnus X region. Near-infrared K -band data are used to revisit the cluster/stellar group identified in previous studies. Radio continuum observations at 610 and 1280 MHz show the presence of a H ii region possibly powered by a star of spectral type B0–B0.5. The cometary morphology of the ionized region is explained by invoking the bow-shock model, where the likely association with a nearby supernova remnant is also explored. A compact radio knot with a non-thermal spectral index is detected towards the centre of the cloud. Mid-infrared data from the Spitzer Legacy Survey of the Cygnus X region show the presence of six Class I young stellar objects inside the cloud. Thermal dust emission in this complex is modelled using Herschel far-infrared data to generate dust temperature and column density maps. Herschel images also show the presence of two clumps in this region, the masses of which are estimated to be ~175 and 30 M . The mass–radius relation and the surface density of the clumps mean that they do not qualify as massive star-forming sites. An overall picture of a runaway star ionizing the cloud and a triggered population of intermediate-mass, Class I sources located towards the cloud centre emerges from this multiwavelength study. Variation in the dust emissivity spectral index is shown to exist in this region and is seen to have an inverse relation with the dust temperature.

Description: We present a modification of the method for reconstructing the stellar velocity ellipsoid (SVE) in disc galaxies. Our version does not need any parametrization of the velocity dispersion profiles and uses only one assumption that the ratio z / R remains constant along the profile or along several pieces of the profile. The method was tested on two galaxies from the sample of other authors and for the first time applied to three lenticular galaxies NGC 1167, NGC 3245 and NGC 4150, as well as to one Sab galaxy NGC 338. We found that for galaxies with a high inclination ( $i 〉 55^\circ \text{--}60^\circ$ ) it is difficult or rather impossible to extract the information about SVE, while for galaxies at an intermediate inclination the procedure of extracting is successful. For NGC 1167 we managed to reconstruct SVE, provided that the value of z / R is piecewise constant. We found z / R = 0.7 for the inner parts of the disc and z / R = 0.3 for the outskirts. We also obtained a rigid constraint on the value of the radial velocity dispersion R for highly inclined galaxies, and tested the result using the asymmetric-drift equation, provided that the gas rotation curve is available.

Description: This paper presents new results from the ongoing study of the unusual Lynx–Cancer void galaxy DDO 68, which has star-forming regions of record low metallicity [12+log (O/H) ~7.14]. The results include the following. (i) A new spectrum and photometry have been obtained with the 6-m SAO RAS telescope (BTA) for the luminous blue variable (LBV = DDO68-V1). Photometric data sets were complemented with others based on the Sloan Digital Sky Survey (SDSS) and the Hubble Space Telescope ( HST ) archive images. (ii) We performed an analysis of the DDO 68 supergiant shell (SGS) and the prominent smaller Hα arcs/shells visible in the HST image coupled with kinematic maps in Hα obtained with the Fabry–Perot interferometer (FPI) at the BTA. (iii) We compiled a list of about 50 of the most luminous stars (–9.1 mag 〈 M V 〈 –6.0 mag) identified from the HST images associated with the star-forming regions with known extremely low O/H. This is intended to pave the path for the current science to be investigated with the next generation of giant telescopes. We have confirmed earlier hints of significant variation of the LBV optical light, deriving its amplitude as V 3.7 mag for the first time. New data suggest that in 2008–2010 the LBV reached M V = –10.5 mag and probably underwent a giant eruption. We argue that the structure of star-forming complexes along the SGS (‘Northern Ring’) perimeter provides evidence for sequential induced star-formation episodes caused by the shell gas instabilities and gravitational collapse. The variability of some luminous extremely metal-poor stars in DDO 68 can currently be monitored with medium-size telescopes at sites with superb seeing.

Description: The number, distribution and properties of dwarf satellites are crucial probes of the physics of galaxy formation at low masses and the response of satellite galaxies to the tidal and gas dynamical effects of their more massive parent. To make progress, it is necessary to augment and solidify the census of dwarf satellites of galaxies outside the Local Group. Müller et al. presented 16 dwarf galaxy candidates near M83, but lacking reliable distances, it is unclear which candidates are M83 satellites. Using red-giant-branch stars from the HST /GHOSTS survey in conjunction with ground-based images from VLT/VIMOS, we confirm that one of the candidates, dw1335-29 – with a projected distance of 26 kpc from M83 and a distance modulus of $(m-M)_0 = 28.5^{+0.3}_{-0.1}$ – is a satellite of M83. We estimate an absolute magnitude M V  = –10.1 ± 0.4, an ellipticity of $0.40^{+0.14}_{-0.22}$ , a half-light radius of $656^{+121}_{-170}$  pc and [Fe/H] = $-1.3^{+0.3}_{-0.4}$ . Owing to dw1335-29's somewhat irregular shape and possible young stars, we classify this galaxy as a dwarf irregular or transition dwarf. This is curious, as with a projected distance of 26 kpc from M83, dw1335-29 is expected to lack recent star formation. Further study of M83's dwarf population will reveal if star formation in its satellites is commonplace (suggesting a lack of a hot gas envelope for M83 that would quench star formation) or rare (suggesting that dw1335-29 has a larger M83-centric distance, and is fortuitously projected to small radii).

Description: We present high-resolution radio continuum observations with the Karl G. Jansky very large array at 6, 8.5, 11.5 and 15 GHz of the double-peaked emission-line galaxy 2MASXJ12032061+1319316. The radio emission has a prominent S-shaped morphology with highly symmetric radio jets that extend over a distance of ~1.5 arcsec (1.74 kpc) on either side of the core of size ~0.1 arcsec (116 pc). The radio jets have a helical structure resembling the precessing jets in the galaxy NGC 326 which has confirmed dual active galactic nuclei (AGN). The nuclear bulge velocity dispersion gives an upper limit of (1.56 ± 0.26) x 10 8 M for the total mass of nuclear black hole(s). We present a simple model of precessing jets in 2MASXJ1203 and find that the precession time-scale is around 10 5 yr: this matches the source lifetime estimate via spectral ageing. We find that the expected supermassive black hole (SMBH) separation corresponding to this time-scale is 0.02 pc. We used the double-peaked emission lines in 2MASXJ1203 to determine an orbital speed for a dual AGN system and the associated jet precession time-scale, which turns out to be more than the Hubble time, making it unfeasible. We conclude that the S-shaped radio jets are due to jet precession caused either by a binary/dual SMBH system, a single SMBH with a tilted accretion disc or a dual AGN system where a close pass of the secondary SMBH in the past has given rise to jet precession.

Description: In any flux-density limited sample of blazars, the distribution of the time-scale modulation factor t '/ t , which quantifies the change in observed time-scales compared to the rest-frame ones due to redshift and relativistic compression follows an exponential distribution with a mean depending on the flux limit of the sample. In this work, we produce the mathematical formalism that allows us to use this information in order to uncover the underlining rest-frame probability density function of measurable time-scales of blazar jets. We extensively test our proposed methodology using a simulated Flat Spectrum Radio Quasar population with a 1.5 Jy flux-density limit in the simple case (where all blazars share the same intrinsic time-scale), in order to identify limits of applicability and potential biases due to observational systematics and sample selection. We find that for monitoring with time intervals between observations longer than ~30 per cent of the intrinsic time-scale under investigation the method loses its ability to produce robust results. For time intervals of ~3 per cent of the intrinsic time-scale, the error of the method is as low as 1 per cent in recovering the intrinsic rest-frame time-scale. We applied our method to rotations of the optical polarization angle of blazars observed by RoboPol. We found that the intrinsic time-scales of the longest duration rotation event in each blazar follows a narrow distribution, well described by a normal distribution with mean 87 d and standard deviation 5 d. We discuss possible interpretations of this result.

Description: About one-third of X-ray-luminous clusters show smooth, Mpc-scale radio emission, known as giant radio haloes. One promising model for radio haloes is Fermi-II acceleration of seed relativistic electrons by compressible turbulence. The origin of these seed electrons has never been fully explored. Here, we integrate the Fokker–Planck equation of the cosmic ray (CR) electron and proton distributions when post-processing cosmological simulations of cluster formation and confront them with radio surface brightness and spectral data of Coma. For standard assumptions, structure formation shocks lead to a seed electron population that produces too centrally concentrated radio emission. Matching observations requires modifying properties of the CR population (rapid streaming; enhanced CR electron acceleration at shocks) or turbulence (increasing turbulent-to-thermal energy density with radius), but at the expense of fine-tuning. In a parameter study, we find that radio properties are exponentially sensitive to the amplitude of turbulence, which is inconsistent with small scatter in scaling relations. This sensitivity is removed if we relate the acceleration time to the turbulent dissipation time. In this case, turbulence above a threshold value provides a fixed amount of amplification; observations could thus potentially constrain the unknown CR seed population. To obtain sufficient acceleration, the turbulent magneto-hydrodynamics cascade has to terminate by transit time damping on CRs, i.e. thermal particles must be scattered by plasma instabilities. Understanding the small scatter in radio halo scaling relations may provide a rich source of insight on plasma processes in clusters.

Description: We measure a combination of gravitational lensing, galaxy clustering and redshift-space distortions (RSDs) called E G . The quantity E G probes both parts of metric potential and is insensitive to galaxy bias and 8 . These properties make it an attractive statistic to test lambda cold dark matter, general relativity and its alternate theories. We have combined CMASS Data Release 11 with CFHTLenS and recent measurements of β from RSD analysis, and find E G ( z  = 0.57) = 0.42 ± 0.056, a 13 per cent measurement in agreement with the prediction of general relativity E G ( z  = 0.57) = 0.396 ± 0.011 using the Planck 2015 cosmological parameters. We have corrected our measurement for various observational and theoretical systematics. Our measurement is consistent with the first measurement of E G using cosmic microwave background lensing in place of galaxy lensing at small scales, but shows 2.8 tension when compared with their final results including large scales. This analysis with future surveys will provide improved statistical error and better control over systematics to test general relativity and its alternate theories.

Description: Using a Bayesian framework, we quantify what current observations imply about the history of the epoch of reionization (EoR). We use a popular, three-parameter EoR model, flexible enough to accommodate a wide range of physically plausible reionization histories. We study the impact of various EoR observations: (i) the optical depth to the CMB measured by Planck 2016; (ii) the dark fraction in the Lyman α and β forests; (iii) the redshift evolution of galactic Lyα emission (so-called ‘Lyα fraction’); (iv) the clustering of Lyα emitters; (v) the IGM damping wing imprint in the spectrum of QSO ULASJ1120+0641; (vi) and the patchy kinetic Sunyaev–Zel'dovich signal. Combined, (i) and (ii) already place interesting constraints on the reionization history, with the epochs corresponding to an average neutral fraction of (75, 50, 25) per cent, constrained at 1 to $z= (9.21^{+1.22 }_{ -1.15}, 8.14^{+1.08 }_{ -1.00}, 7.26^{+1.13 }_{ -0.96})$ . Folding-in more model-dependent EoR observations [(iii)–(vi)], strengthens these constraints by tens of per cent, at the cost of a decrease in the likelihood of the best-fitting model, driven mostly by (iii). The tightest constraints come from (v). Unfortunately, no current observational set is sufficient to break degeneracies and constrain the astrophysical EoR parameters. However, model-dependent priors on the EoR parameters themselves can be used to set tight limits by excluding regions of parameter space with strong degeneracies. Motivated by recent observations of z ~ 7 faint, lensed galaxies, we show how a conservative upper limit on the virial temperature of haloes which host reionizing galaxies can constrain the escape fraction of ionizing photons to $f_{\rm esc} = 0.14^{+0.26 }_{ -0.09}$ .

Description: We present new time-resolved photometry of 74 cataclysmic variables (CVs), 47 of which are eclipsing. Thirteen of these eclipsing systems are newly discovered. For all 47 eclipsing systems, we show high cadence (1–20 s) light curves obtained with the high-speed cameras ULTRACAM and ULTRASPEC. We provide new or refined ephemerides, and supply mid-eclipse times for all observed eclipses. We assess the potential for light-curve modelling of all 47 eclipsing systems to determine their system parameters, finding 20 systems that appear to be suitable for future study. Systems of particular interest include V713 Cep, in which we observed a temporary switching-off of accretion; and ASASSN-14mv and CSS111019:233313–155744, which both have orbital periods well below the CV period minimum. The short orbital periods and light-curve shapes suggest that they may be double degenerate (AM CVn) systems or CVs with evolved donor stars.

Description: We have used the 610-MHz receivers of the Giant Metrewave Radio Telescope (GMRT) to detect associated H i 21-cm absorption from the z  = 1.2230 blazar TXS 1954+513. The GMRT H i 21-cm absorption is likely to arise against either the milliarcsecond-scale core or the one-sided milliarcsecond-scale radio jet, and is blueshifted by 328 km s –1 from the blazar redshift. This is consistent with a scenario in which the H i cloud giving rise to the absorption is being driven outwards by the radio jet. The integrated H i 21-cm optical depth is (0.716 ± 0.037) km s –1 , implying a high H i column density, $N_{\rm H\small {I}} = (1.305 \pm 0.067) \times ({ T_{\rm s}/100\,{\rm K}}) \times 10^{20}$  cm –2 , for an assumed H i spin temperature of 100 K. We use Nickel Telescope photometry of TXS 1954+513 to infer a high rest-frame 1216 Å luminosity of (4.1 ± 1.2)  x  10 23 W Hz –1 . The z  = 1.2230 absorber towards TXS 1954+513 is only the fifth case of a detection of associated H i 21-cm absorption at z  〉 1, and is also the first case of such a detection towards an active galactic nucleus (AGN) with a rest-frame ultraviolet (UV) luminosity 〉〉10 23 W Hz –1 , demonstrating that neutral hydrogen can survive in AGN environments in the presence of high UV luminosities.

Description: Recent photometric analyses of the colour–magnitude diagrams of young massive clusters (YMCs) have found evidence for splitting in the main sequence and extended main-sequence turn-offs, both of which have been suggested to be caused by stellar rotation. Comparison of the observed main-sequence splitting with models has led various authors to suggest a rather extreme stellar rotation distribution, with a minority (10–30 per cent) of stars with low rotational velocities and the remainder (70–90 per cent) of stars rotating near the critical rotation (i.e. near break-up). We test this hypothesis by searching for Be stars within two YMCs in the Large Magellanic Cloud (NGC 1850 and NGC 1856), which are thought to be critically rotating stars with decretion discs that are (partially) ionized by their host stars. In both clusters, we detect large populations of Be stars at the main-sequence turn-off (~30–60 per cent of stars), which supports previous suggestions of large populations of rapidly rotating stars within massive clusters.

Description: The mass of the Local Group (LG) is a crucial parameter for galaxy formation theories. However, its observational determination is challenging – its mass budget is dominated by dark matter that cannot be directly observed. To meet this end, the posterior distributions of the LG and its massive constituents have been constructed by means of constrained and random cosmological simulations. Two priors are assumed – the cold dark matter model that is used to set up the simulations, and an LG model that encodes the observational knowledge of the LG and is used to select LG-like objects from the simulations. The constrained simulations are designed to reproduce the local cosmography as it is imprinted on to the Cosmicflows-2 data base of velocities. Several prescriptions are used to define the LG model, focusing in particular on different recent estimates of the tangential velocity of M31. It is found that (a) different v tan choices affect the peak mass values up to a factor of 2, and change mass ratios of M M31 to M MW by up to 20 per cent; (b) constrained simulations yield more sharply peaked posterior distributions compared with the random ones; (c) LG mass estimates are found to be smaller than those found using the timing argument; (d) preferred Milky Way masses lie in the range of (0.6–0.8) x 10 12  M ; whereas (e) M M31 is found to vary between (1.0–2.0) x 10 12  M , with a strong dependence on the v tan values used.

Description: Statistical analysis of Faraday rotation measure (RM) maps of the intracluster medium (ICM) of galaxy clusters provides a unique tool to evaluate some spatial features of the magnetic fields there. Its combination with numerical simulations of magnetohydrodynamic (MHD) turbulence allows the diagnosis of the ICM turbulence. Being the ICM plasma weakly collisional, the thermal velocity distribution of the particles naturally develops anisotropies as a consequence of the large-scale motions and the conservation of the magnetic moment of the charged particles. A previous study ( Paper I ) analysed the impact of large-scale thermal anisotropy on the statistics of RM maps synthesized from simulations of turbulence; these simulations employed a collisionless MHD model that considered a tensor pressure with uniform anisotropy. In this work, we extend that analysis to a collisionless MHD model in which the thermal anisotropy develops according to the conservation of the magnetic moment of the thermal particles. We also consider the effect of anisotropy relaxation caused by the microscale mirror and firehose instabilities. We show that if the relaxation rate is fast enough to keep the anisotropy limited by the threshold values of the instabilities, the dispersion and power spectrum of the RM maps are indistinguishable from those obtained from collisional MHD. Otherwise, there is a reduction in the dispersion and steepening of the power spectrum of the RM maps (compared to the collisional case). Considering the first scenario, the use of collisional MHD simulations for modelling the RM statistics in the ICM becomes better justified.

Description: A key challenge in understanding the feedback mechanism of active galactic nucleus (AGN) in Brightest Cluster Galaxies (BCGs) is the inherent rarity of catching an AGN during its strong outburst phase. This is exacerbated by the ambiguity of differentiating between AGN and clusters in X-ray observations. If there is evidence for an AGN then the X-ray emission is commonly assumed to be dominated by the AGN emission, introducing a selection effect against the detection of AGN in BCGs. In order to recover these ‘missing’ clusters, we systematically investigate the colour–magnitude relation around some ~3500 ROSAT All-Sky Survey selected AGN, looking for signs of a cluster red sequence. Amongst our 22 candidate systems, we independently rediscover several confirmed systems, where a strong AGN resides in a central galaxy. We compare the X-ray luminosity to red sequence richness distribution of our AGN candidate systems with that of a similarly selected comparison sample of ~1000 confirmed clusters and identify seven ‘best’ candidates (all of which are BL Lac objects), where the X-ray flux is likely to be a comparable mix between cluster and AGN emission. We confirm that the colours of the red sequence are consistent with the redshift of the AGN, that the colours of the AGN host galaxy are consistent with AGN, and, by comparing their luminosities with those from our comparison clusters, confirm that the AGN hosts are consistent with BCGs.

Description: Prior statistical knowledge of atmospheric turbulence is essential for designing, optimizing and evaluating tomographic adaptive optics systems. We present the statistics of the vertical profiles of $C_N^2$ and the outer scale at Maunakea estimated using a SLOpe Detection And Ranging (SLODAR) method from on-sky telemetry taken by a multi-object adaptive optics (MOAO) demonstrator, called RAVEN, on the Subaru telescope. In our SLODAR method, the profiles are estimated by fitting the theoretical autocorrelations and cross-correlations of measurements from multiple Shack–Haltmann wavefront sensors to the observed correlations via the non-linear Levenberg–Marquardt Algorithm (LMA). The analytical derivatives of the spatial phase structure function with respect to its parameters for the LMA are also developed. From a total of 12 nights in the summer season, a large ground $C_N^2$ fraction of 54.3 per cent is found, with median estimated seeing of 0.460 arcsec. This median seeing value is below the results for Maunakea from the literature (0.6–0.7 arcsec). The average $C_N^2$ profile is in good agreement with results from the literature, except for the ground layer. The median value of the outer scale is 25.5 m and the outer scale is larger at higher altitudes; these trends of the outer scale are consistent with findings in the literature.

Description: Braking index measurements offer the opportunity to explore the processes affecting the long-term spin evolution of pulsars and possible evolutionary connections between the various pulsar populations. In most cases, such measurements are difficult because of the presence of short-term phenomena, such as glitches and timing noise, which obscure the long-term trends. In particular, recoveries from large glitches are the main obstacle to measuring the braking indices of young pulsars like the Vela and Crab pulsars. We present a new method to overcome this problem and report on braking index measurements for the Vela-like pulsars, PSR B1800–21 and PSR B1823–13, together with an updated measurement for Vela. Additionally, the use of the method is extended to six more young glitching pulsars observed at Jodrell Bank Observatory and we are able to estimate four new braking indices. Values of braking indices describe the long-term evolution of the pulsars across the P – $\dot{P}$ diagram. Despite some measurements being affected by considerable uncertainties, there is evidence for a common trend among young glitching pulsars, characterized by low braking indices n ≤ 2. Such values introduce a new variant in the evolution of young pulsars, and their relationship with other populations in the P – $\dot{P}$ diagram, and imply that these pulsars could be a few times older than indicated by standard formulae. In this context, we analyse the case of PSR B1757–24 and conclude that the pulsar could be old enough to be related to the supernova remnant G5.4–1.2. Between glitches, the short-term evolution of Vela-like pulsars is characterized by large interglitch braking indices n ig  〉 10. We interpret both short- and long-term trends as signatures of the large glitch activity, and speculate that they are driven by short-term post-glitch re-coupling and a cumulative long-term decoupling of superfluid to the rotation of the star.

Description: We present the results of a photometric and spectroscopic analysis of the Galactic Bulge Survey X-ray source CXOGBS J174954.5–294335 (hereafter, referred to as CX19). CX19 is a long period, eclipsing intermediate polar-type cataclysmic variable with broad, single-peaked Balmer and Paschen emission lines along with He ii 4686 and Bowen blend emission features. With coverage of one full and two partial eclipses and archival photometry, we determine the ephemeris for CX19 to be HJD(eclipse) = 2455691.8581(5) + 0.358704(2) x N . We also recovered the white dwarf spin period of P spin = 503.32(3) s that gives a P spin / P orb = 0.016(6), comparable to several confirmed, long-period intermediate polars. CX19 also shows a clear X-ray eclipse in the 0.3–8.0 keV range observed with Chandra . Two optical outbursts were observed lasting between 6 and 8 h (lower limits) reaching ~1.3 mag in amplitude. The outbursts, both in duration and magnitude, the accretion disc-dominated spectra and hard X-ray emission are reminiscent of the intermediate polar V1223 Sgr sharing many of the same characteristics. If we assume a main-sequence companion, we estimate the donor to be an early G-type star and find a minimum distance of d 2.1 kpc and a 0.5–10.0 keV X-ray luminosity upper limit of 2.0 x 10 33  erg s –1 . Such an X-ray luminosity is consistent with a white dwarf accretor in a magnetic cataclysmic variable system. To date, CX19 is only the second deeply eclipsing intermediate polar with X-ray eclipses and the first that is optically accessible.

Description: Absolute cross-sections for the K -shell photoionization of Be-like (O 4 + ) and Li-like (O 5 + ) atomic oxygen ions were measured for the first time (in their respective K -shell regions) by employing the ion–photon merged-beam technique at the SOLEIL synchrotron-radiation facility in Saint-Aubin, France. High-resolution spectroscopy with E / E 3200 (170 meV, full width at half-maximum) was achieved with photon energy from 550 to 670 eV. Rich resonance structure observed in the experimental spectra is analysed using the R-matrix with pseudo-states (RMPS) method. Results are also compared with the screening constant by unit nuclear charge (SCUNC) calculations. We characterize and identify the strong 1s -〉 2p resonances for both ions and the weaker 1s -〉 n p resonances ( n ≥ 3) observed in the K -shell spectra of O 4 + .

Description: We use the concept of the spiral rotation curves universality to investigate the luminous and dark matter properties of the dwarf disc galaxies in the local volume (size ~11 Mpc). Our sample includes 36 objects with rotation curves carefully selected from the literature. We find that, despite the large variations of our sample in luminosities (~2 of dex), the rotation curves in specifically normalized units, look all alike and lead to the lower mass version of the universal rotation curve of spiral galaxies found in Persic et al. We mass model the double normalized universal rotation curve V ( R / R opt )/ V opt of dwarf disc galaxies: the results show that these systems are totally dominated by dark matter whose density shows a core size between 2 and 3 stellar disc scalelengths. Similar to galaxies of different Hubble types and luminosities, the core radius r 0 and the central density 0 of the dark matter halo of these objects are related by 0 r 0  ~ 100 M pc –2 . The structural properties of the dark and luminous matter emerge very well correlated. In addition, to describe these relations, we need to introduce a new parameter, measuring the compactness of light distribution of a (dwarf) disc galaxy. These structural properties also indicate that there is no evidence of abrupt decline at the faint end of the baryonic to halo mass relation. Finally, we find that the distributions of the stellar disc and its dark matter halo are closely related.

Description: New spectra of 81 ultracool dwarfs (spectral types M7 and later) are discussed. Spectral classifications of 49 objects are available in the literature, while 32 objects are newly classified. The known spectral types were used to test an automated classification scheme, which relies primarily on template fitting, supplemented by matching of spectral indices calibrated against the template spectra. An attempt was made to quantify the uncertainty in the spectral types, which is generally better than two subclasses. Objects for which spectral types differ by more than one subclass from the literature classifications are discussed individually. Discrepancies between automated classifications based on, respectively, template fitting and spectral index matching, may be useful for flagging objects with unusual spectra. Aside from the 32 first-time classifications, alternative classifications are presented for 32 previously classified dwarfs. Very large (equivalent width greater than 130 Å) Hα flares are reported for the known ultracool dwarf binary 2MASS J15200224–4422419; curiously, the object does not appear to have quiescent emission lines. Non-zero equivalent-width measurements are listed for a further 29 objects.

Description: We present a photometric study of PGC 1000714, a galaxy resembling Hoag's Object with a complete detached outer ring, that has not yet been described in the literature. Since the Hoag-type galaxies are extremely rare and peculiar systems, it is necessary to increase the sample of known objects by performing the detailed studies on the possible candidates to derive conclusions about their nature, evolution and systematic properties. We therefore performed surface photometry of the central body by using the archival near-UV, infrared data and the new optical data ( BVRI ). This current work has revealed for the first time an elliptical galaxy with two fairly round rings. The central body follows well a r 1/4 light profile, with no sign of a bar or stellar disc. By reconstructing the observed spectral energy distribution, we recover the stellar population properties of the central body and the outer ring. Our work suggests different formation histories for the galaxy components. Possible origins of the galaxy are discussed, and we conclude that a recent accretion event is the most plausible scenario that accounts for the observational characteristic of PGC 1000714.

Description: A novel technique for detecting Lagrangian vortices is applied to a helical magnetohydrodynamic dynamo simulation. The vortices are given by tubular level surfaces of the Lagrangian averaged vorticity deviation, the trajectory integral of the normed difference of the vorticity from its spatial mean. This simple method is objective, i.e. invariant under time-dependent rotations and translations of the coordinate frame. We also adapt the technique to use it on magnetic fields and propose the method of integrated averaged current deviation to determine precisely the boundary of magnetic vortices. The relevance of the results for the study of vortices in solar plasmas is discussed.

Description: We present a structural study of 182 obscured active galactic nuclei (AGNs) at z  ≤ 1.5, selected in the Cosmic Evolution Survey field from their extreme infrared to X-ray luminosity ratio and their negligible emission at optical wavelengths. We fit optical to far-infrared spectral energy distributions and analyse deep Hubble Space Telescope imaging to derive the physical and morphological properties of their host galaxies. We find that such galaxies are more compact than normal star-forming sources at similar redshift and stellar mass, and we show that it is not an observational bias related to the emission of the AGN. Based on the distribution of their UVJ colours, we also argue that this increased compactness is not due to the additional contribution of a passive bulge. We thus postulate that a vast majority of obscured AGNs reside in galaxies undergoing dynamical compaction, similar to processes recently invoked to explain the formation of compact star-forming sources at high redshift.

Description: We analyse the spectra of black hole (BH) and neutron star (NS) X-ray binaries (XBs) in the hard state using archival RXTE observations. We find that there is a clear dichotomy in the strength of Comptonization between NS and BH sources, as measured by both the Compton y -parameter and the amplification factor A , with distinct groups of BH and NS XBs separated at y  ~ 0.9 and A  ~ 3. The electron temperature kT e can occupy a broad range in BH systems, from kT e  ~ 30 to 200 keV, whereas for NSs kT e is peaked at ~15–25 keV, but can extend to higher values. The difference between BHs and NSs in y implies that kT e is higher at a given optical depth for BH XBs. Our results also imply that for NS systems the accreting material loses ~1/2–2/3 of its energy through Comptonization in the corona. The remaining energy is released on the surface of the NS, making it a powerful source of soft radiation, which alters the properties of the Comptonizing corona. Finally, we find evidence at the ~2.4 confidence level that Comptonization parameters may be correlated with the NS spin, whereas no correlation with the BH spin is found. Our results highlight a further observational distinction between BH and NS XBs, which is a consequence of NSs possessing a physical surface.

Description: We present spectral line mapping observations towards four massive star-forming regions – Cepheus A, DR21S, S76E and G34.26+0.15 – with the IRAM 30-m telescope at the 2 and 3 mm bands. In total, 396 spectral lines from 51 molecules, one helium recombination line, 10 hydrogen recombination lines and 16 unidentified lines were detected in these four sources. An emission line of nitrosyl cyanide (ONCN, 14 0, 14 –13 0, 13 ) was detected in G34.26+0.15, as the first detection in massive star-forming regions. We found that c –C 3 H 2 and NH 2 D show enhancement in shocked regions, as suggested by the evidence of SiO and/or SO emission. The column density and rotational temperature of CH 3 CN were estimated with the rotational diagram method for all four sources. Isotope abundance ratios of 12 C/ 13 C were derived using HC 3 N and its 13 C isotopologue, which were around 40 in all four massive star-forming regions and slightly lower than the local interstellar value (~65). The 14 N/ 15 N and 16 O/ 18 O abundance ratios in these sources were also derived using the double isotopic method, which were slightly lower than in the local interstellar medium. Except for Cep A, the 33 S/ 34 S ratios in the other three targets were derived, which were similar to that in the local interstellar medium. The column density ratios of N(DCN)/N(HCN) and N(DCO + )/N(HCO + ) in these sources were more than two orders of magnitude higher than the elemental [D]/[H] ratio, which is 1.5 x 10 –5 . Our results show that the later stage sources, G34.26+0.15 in particular, present more molecular species than earlier stage sources. Evidence of shock activity is seen in all stages studied.

Description: Measurements of the galaxy stellar mass function are crucial to understand the formation of galaxies in the Universe. In a hierarchical clustering paradigm, it is plausible that there is a connection between the properties of galaxies and their environments. Evidence for environmental trends has been established in the local Universe. The Dark Energy Survey (DES) provides large photometric data sets that enable further investigation of the assembly of mass. In this study, we use ~3.2 million galaxies from the (South Pole Telescope) SPT-East field in the DES science verification (SV) data set. From grizY photometry, we derive galaxy stellar masses and absolute magnitudes, and determine the errors on these properties using Monte Carlo simulations using the full photometric redshift probability distributions. We compute galaxy environments using a fixed conical aperture for a range of scales. We construct galaxy environment probability distribution functions and investigate the dependence of the environment errors on the aperture parameters. We compute the environment components of the galaxy stellar mass function for the redshift range 0.15 〈 z 〈 1.05. For z 〈 0.75, we find that the fraction of massive galaxies is larger in high-density environment than in low-density environments. We show that the low-density and high-density components converge with increasing redshift up to z ~ 1.0 where the shapes of the mass function components are indistinguishable. Our study shows how high-density structures build up around massive galaxies through cosmic time.

Description: We present new observations of the nebula around the Magellanic candidate Luminous Blue Variable S61. These comprise high-resolution data acquired with the Australia Telescope Compact Array (ATCA), the Atacama Large Millimetre/Submillimetre Array (ALMA), and the VLT Imager and Spectrometer for mid Infrared (VISIR) at the Very Large Telescope. The nebula was detected only in the radio, up to 17 GHz. The 17 GHz ATCA map, with 0.8 arcsec resolution, allowed a morphological comparison with the $\rm H\rm \alpha$ Hubble Space Telescope image. The radio nebula resembles a spherical shell, as in the optical. The spectral index map indicates that the radio emission is due to free–free transitions in the ionized, optically thin gas, but there are hints of inhomogeneities. We present our new public code R hocube to model 3D density distributions and determine via Bayesian inference the nebula's geometric parameters. We applied the code to model the electron density distribution in the S61 nebula. We found that different distributions fit the data, but all of them converge to the same ionized mass, ~ 0.1 M , which is an order of magnitude smaller than previous estimates. We show how the nebula models can be used to derive the mass-loss history with high-temporal resolution. The nebula was probably formed through stellar winds, rather than eruptions. From the ALMA and VISIR non-detections, plus the derived extinction map, we deduce that the infrared emission observed by space telescopes must arise from extended, diffuse dust within the ionized region.

Description: We report on the first focused hard X-ray view of the absorbed supergiant system IGR J18027–2016 performed with the Nuclear Spectroscopic Telescope Array observatory. The pulsations are clearly detected with a period of P spin  = 139.866(1) s and a pulse fraction of about 50–60 per cent at energies from 3 to 80 keV. The source demonstrates an approximately constant X-ray luminosity on a time-scale of more than dozen years with an average spin-down rate of $\dot{P}\simeq 6\times 10^{-10}$ s s –1 . This behaviour of the pulsar can be explained in terms of the wind accretion model in the settling regime. The detailed spectral analysis at energies above 10 keV was performed for the first time and revealed a possible cyclotron absorption feature at energy ~23 keV. This energy corresponds to the magnetic field B ~= 3  x  10 12  G at the surface of the neutron star, which is typical for X-ray pulsars.

Description: We measured the chromospheric activity of the four hot Jupiter hosts WASP-43, WASP-51/HAT-P-30, WASP-72 and WASP-103 to search for anomalous values caused by the close-in companions. The Mount Wilson Ca ii H & K S -index was calculated for each star using observations taken with the Robert Stobie Spectrograph at the Southern African Large Telescope. The activity level of WASP-43 is anomalously high relative to its age and falls among the highest values of all known main-sequence stars. We found marginal evidence that the activity of WASP-103 is also higher than expected from the system age. We suggest that for WASP-43 and WASP-103 star–planet interactions (SPI) may enhance the Ca ii H & K core emission. The activity levels of WASP-51/HAT-P-30 and WASP-72 are anomalously low, with the latter falling below the basal envelope for both main-sequence and evolved stars. This can be attributed to circumstellar absorption due to planetary mass-loss, though absorption in the interstellar medium may contribute. A quarter of known short-period planet hosts exhibit anomalously low activity levels, including systems with hot Jupiters and low-mass companions. Since SPI can elevate and absorption can suppress the observed chromospheric activity of stars with close-in planets, their Ca ii H & K activity levels are an unreliable age indicator. Systems where the activity is depressed by absorption from planetary mass-loss are key targets for examining planet compositions through transmission spectroscopy.

Description: We perform a tomographic baryon acoustic oscillations (BAO) analysis using the monopole, quadrupole and hexadecapole of the redshift-space galaxy power spectrum measured from the pre-reconstructed combined galaxy sample of the completed Sloan Digital Sky Survey Baryon Oscillation Spectroscopic Survey (BOSS) Data Release12 covering the redshift range of 0.20 〈  z  〈 0.75. By allowing for overlap between neighbouring redshift slices, we successfully obtained the isotropic and anisotropic BAO distance measurements within nine redshift slices to a precision of 1.5–3.4 per cent for D V / r d , 1.8–4.2 per cent for D A / r d and 3.7–7.5 per cent for H r d , depending on effective redshifts. We provide our BAO measurement of D A / r d and H r d with the full covariance matrix, which can be used for cosmological implications. Our measurements are consistent with those presented in Alam et al., in which the BAO distances are measured at three effective redshifts. We constrain dark energy parameters using our measurements and find an improvement of the Figure-of-Merit of dark energy in general due to the temporal BAO information resolved. This paper is a part of a set that analyses the final galaxy clustering data set from BOSS.

Description: The effective temperature ( T eff ) of the radiation field of the ionizing star(s) of a large sample of extragalactic H ii regions was estimated using the R = log([O ii ] (3726 + 29)/[O iii ] 5007) index. We used a grid of photoionization models to calibrate the T eff – R relation finding that it has a strong dependence with the ionizing parameter, while it shows a weak direct dependence with the metallicity (variations in Z imply variations in U ) of both the stellar atmosphere of the ionizing star and the gas phase of the H ii region. Since the R index varies slightly with the T eff for values larger than 40 kK, the R index can be used to derive the T eff in the 30–40 kK range. A large fraction of the ionization parameter variation is due to differences in the temperature of the ionizing stars and then the use of the (relatively) low T eff dependent S 2 = [S ii ] (6717 + 31)/Hα emission-line ratio to derive the ionization parameter is preferable over others in the literature. We propose linear metallicity dependent relationships between S 2 and U . T eff and metallicity estimations for a sample of 865 H ii regions, whose emission-line intensities were compiled from the literature, do not show any T eff – Z correlation. On the other hand, it seems to be hints of the presence of an anticorrelation between T eff – U . We found that the majority of the studied H ii regions (~87 per cent) present T eff values in the range between 37 and 40 kK, with an average value of 38.5(±1) kK. We also studied the variation of T eff as a function of the galactocentric distance for 14 spiral galaxies. Our results are in agreement with the idea of the existence of positive T eff gradients along the disc of spiral galaxies.

Description: We investigate the nature of so-called low T / W dynamical instability in a differentially rotating star, by focusing on the role played by the corotation radius of the unstable oscillation modes. A one-dimensional model of linear perturbation, which neglects dependence of variables on the coordinate along the rotational axis of the star, is solved to obtain stable and unstable eigenmodes. A linear eigenmode having a corotation radius, at which azimuthal pattern speed of the mode coincides with the stellar angular velocity, is categorized to either a complex (growing or damping) mode or a purely real mode belonging to a continuous spectrum of frequency. We compute canonical angular momentum and its flux to study eigenmodes with corotation radius. In a dynamically unstable mode, sound wave transports its angular momentum in such a way that the absolute value of the angular momentum is increased on both sides of the corotation radius. We further evaluate growth of amplitude of reflected sound wave incident to a corotation point, and find that the overreflection of the wave and the trapping of it between the corotation radius and the surface of the star may qualitatively explain dependences of eigenfrequencies on the stellar differential rotation. The results suggest that the low T / W instability may be caused by overreflection of sound waves trapped mainly between the surface of the star and a corotation radius.

Description: We present a numerical method that evolves a two-temperature, magnetized, radiative, accretion flow around a black hole, within the framework of general relativistic radiation magnetohydrodynamics. As implemented in the code koral , the gas consists of two sub-components – ions and electrons – which share the same dynamics but experience independent, relativistically consistent, thermodynamical evolution. The electrons and ions are heated independently according to a prescription from the literature for magnetohydrodynamical turbulent dissipation. Energy exchange between the particle species via Coulomb collisions is included. In addition, electrons gain and lose energy and momentum by absorbing and emitting synchrotron and bremsstrahlung radiation and through Compton scattering. All evolution equations are handled within a fully covariant framework in the relativistic fixed-metric space–time of the black hole. Numerical results are presented for five models of low-luminosity black hole accretion. In the case of a model with a mass accretion rate $\dot{M}\sim 4\times 10^{-8} \dot{M}_{\rm Edd}$ , we find that radiation has a negligible effect on either the dynamics or the thermodynamics of the accreting gas. In contrast, a model with a larger $\dot{M}\sim 4\times 10^{-4} \dot{M}_{\rm Edd}$ behaves very differently. The accreting gas is much cooler and the flow is geometrically less thick, though it is not quite a thin accretion disc.

Description: The plasma haloes filling massive galaxies, groups and clusters are shaped by active galactic nucleus (AGN) heating and subsonic turbulence ( v  ~ 150 km s –1 ), as probed by Hitomi . Novel 3D high-resolution simulations show the soft X-ray, keV hot plasma cools rapidly via radiative emission at the high-density interface of the turbulent eddies, stimulating a top-down condensation cascade of warm 10 4  K filaments. The kpc-scale ionized (optical/ultraviolet) filaments form a skin enveloping the neutral filaments (optical/infrared/21 cm). The peaks of the warm filaments further condense into cold molecular clouds (〈50 K; radio) with total mass of several 10 7 M and inheriting the turbulent kinematics. In the core, the clouds collide inelastically, mixing angular momentum and leading to Chaotic Cold Accretion (CCA). The black hole accretion rate (BHAR) can be modelled via quasi-spherical viscous accretion, $\dot{M}_\bullet \propto \nu _{\rm c}$ , with clump collisional viscosity c c v and c ~ 100 pc. Beyond the core, pressure torques shape the angular momentum transport. In CCA, the BHAR is recurrently boosted up to 2 dex compared with the disc evolution, which arises as turbulence becomes subdominant. With negligible rotation too, compressional heating inhibits the molecular phase. The CCA BHAR distribution is lognormal with pink noise, f –1 power spectrum characteristic of fractal phenomena. Such chaotic fluctuations can explain the rapid luminosity variability of AGN and high-mass X-ray binaries. An improved criterium to trace non-linear condensation is proposed: v / v cool 1. The three-phase CCA reproduces key observations of cospatial multiphase gas in massive galaxies, including Chandra X-ray images, SOAR Hα filaments and kinematics, Herschel [C + ] emission and ALMA molecular associations. CCA plays important role in AGN feedback and unification, the evolution of BHs, galaxies and clusters.

Description: Galaxy interactions are thought to be one of the main triggers of active galactic nuclei (AGN), especially at high luminosities, where the accreted gas mass during the AGN lifetime is substantial. Evidence for a connection between mergers and AGN, however, remains mixed. Possible triggering mechanisms remain particularly poorly understood for luminous AGN, which are thought to require triggering by major mergers, rather than secular processes. We analyse the host galaxies of a sample of 20 optically and X-ray selected luminous AGN (log( L bol [erg s –1 ]) 〉 45) at z  ~ 0.6 using Hubble Space Telescope Wide Field Camera 3 data in the F 160 W / H band. 15/20 sources have resolved host galaxies. We create a control sample of mock AGN by matching the AGN host galaxies to a control sample of non-AGN galaxies. Visual signs of disturbances are found in about 25 per cent of sources in both the AGN hosts and control galaxies. Using both visual classification and quantitative morphology measures, we show that the levels of disturbance are not enhanced when compared to a matched control sample. We find no signs that major mergers play a dominant role in triggering AGN at high luminosities, suggesting that minor mergers and secular processes dominate AGN triggering up to the highest AGN luminosities. The upper limit on the enhanced fraction of major mergers is ≤20 per cent. While major mergers might increase the incidence of luminous AGN, they are not the prevalent triggering mechanism in the population of unobscured AGN.

Description: The recent detection of anions in the interstellar medium has shown that they exist in a variety of astrophysical environments – circumstellar envelopes, cold dense molecular clouds and star-forming regions. Both radiative and collisional processes contribute to molecular excitation and de-excitation in these regions so that the ‘local thermodynamic equilibrium’ approximation, where collisions cause the gas to behave thermally, is not generally valid. Therefore, along with radiative coefficients, collisional excitation rate coefficients are needed to accurately model the anionic emission from these environments. We focus on the calculation of state-to-state rate coefficients of the C 6 H – molecule in its ground vibrational state in collisions with para-H 2 , ortho-H 2 and He using new potential energy surfaces. Dynamical calculations for the pure rotational excitation of C 6 H – were performed for the first 11 rotational levels (up to j 1 = 10) using the close-coupling method, while the coupled-states approximation was used to extend the H 2 rate coefficients to j 1 = 30, where j 1 is the angular momentum quantum number of C 6 H – . State-to-state rate coefficients were obtained for temperatures ranging from 2 to 100 K. The rate coefficients for H 2 collisions for j 1 = –1 transitions are of the order of 10 –10  cm 3  s –1 , a factor of 2 to 3 greater than those of He. Propensity rules are discussed. The collisional excitation rate coefficients produced here impact astrophysical modelling since they are required for obtaining accurate C 6 H – level populations and line emission for regions that contain anions.

Description: I start by providing an updated summary of the penalized pixel-fitting ( ppxf ) method that is used to extract the stellar and gas kinematics, as well as the stellar population of galaxies, via full spectrum fitting. I then focus on the problem of extracting the kinematics when the velocity dispersion is smaller than the velocity sampling V that is generally, by design, close to the instrumental dispersion inst . The standard approach consists of convolving templates with a discretized kernel, while fitting for its parameters. This is obviously very inaccurate when V /2, due to undersampling. Oversampling can prevent this, but it has drawbacks. Here I present a more accurate and efficient alternative. It avoids the evaluation of the undersampled kernel and instead directly computes its well-sampled analytic Fourier transform, for use with the convolution theorem. A simple analytic transform exists when the kernel is described by the popular Gauss–Hermite parametrization (which includes the Gaussian as special case) for the line-of-sight velocity distribution. I describe how this idea was implemented in a significant upgrade to the publicly available ppxf software. The key advantage of the new approach is that it provides accurate velocities regardless of . This is important e.g. for spectroscopic surveys targeting galaxies with 〈〈 inst , for galaxy redshift determinations or for measuring line-of-sight velocities of individual stars. The proposed method could also be used to fix Gaussian convolution algorithms used in today's popular software packages.

Description: We constrain the H  i photoionization rate $(\Gamma _{\rm H\, {\small I}})$ at z 0.45 by comparing the flux probability distribution function and power spectrum of the Lyα forest data along 82 Quasi-Stellar Object (QSO) sightlines obtained using Cosmic Origins Spectrograph with models generated from smoothed particle hydrodynamic simulations. We have developed a module named ‘Code for Ionization and Temperature Evolution ( cite )’ for calculating the intergalactic medium (IGM) temperature evolution from high to low redshifts by post-processing the gadget-2 simulation outputs. Our method, that produces results consistent with other simulations, is computationally less expensive thus allowing us to explore a large parameter space. It also allows rigorous estimation of the error covariance matrix for various statistical quantities of interest. We find that the best-fitting $\Gamma _{\rm H\,{\small I}}(z)$ increases with z and follows (4 ± 0.1)  x  10 –14 (1 +  z ) 4.99 ± 0.12  s –1 . At any given z , the typical uncertainties $\Delta \Gamma _{\rm H\,{\small I}} / \Gamma _{\rm H\,{\small I}}$ are ~25 per cent that contains not only the statistical errors but also those arising from possible degeneracy with the thermal history of the IGM and cosmological parameters and uncertainties in fitting the QSO continuum. These values of $\Gamma _{\rm H\,{\small I}}$ favour the scenario where only QSOs contribute to the ionizing background at z  〈 2. Our derived 3 upper limit on average escape fraction is 0.008, consistent with measurements of low- z galaxies.

Description: We present adaptive optics (AO) assisted SINFONI integral field unit (IFU) spectroscopy of 11 Hα emitting galaxies selected from the High- Z Emission Line Survey (HiZELS). We obtain spatially resolved dynamics on ~kpc-scales of star-forming galaxies [stellar mass M *  = 10 9.5 – 10.5  M and star formation rate (SFR) = 2–30 M  yr –1 ] near the peak of the cosmic star formation rate history. Combining these observations with our previous SINFONI-HiZELS campaign, we construct a sample of 20 homogeneously selected galaxies with IFU AO-aided observations – the ‘SHiZELS’ survey, with roughly equal number of galaxies per redshift slice, at z  = 0.8, 1.47 and 2.23. We measure the dynamics and identify the major kinematic axis by modelling their velocity fields to extract rotational curves and infer their inclination-corrected rotational velocities. We explore the stellar mass Tully–Fisher relationship, finding that galaxies with higher velocity dispersions tend to deviate from this relation. Using kinemetry analyses, we find that galaxy interactions might be the dominant mechanism controlling the star formation activity at z  = 2.23 but they become gradually less important down to z  = 0.8. Metallicity gradients derived from the [N ii ]/Hα emission line ratio show a median negative gradient for the SHiZELS survey of log(O/H)/ R = –0.026 ± 0.008 dex kpc –1 . We find that metal-rich galaxies tend to show negative gradients, whereas metal-poor galaxies tend to exhibit positive metallicity gradients. This result suggests that the accretion of pristine gas in the periphery of galaxies plays an important role in replenishing the gas in ‘typical’ star-forming galaxies.

Description: In response to a recently reported observation of evidence for two classes of Type Ia supernovae (SNe Ia) distinguished by their brightness in the rest-frame near-ultraviolet (NUV), we search for the phenomenon in publicly available light-curve data. We use the snana supernova analysis package to simulate SN Ia light curves in the Sloan Digital Sky Survey (SDSS) Supernova Search and the Supernova Legacy Survey (SNLS) with a model of two distinct ultraviolet classes of SNe Ia and a conventional model with a single broad distribution of SN-Ia ultraviolet brightnesses. We compare simulated distributions of rest-frame colours with these two models to those observed in 158 SNe Ia in the SDSS and SNLS data. The SNLS sample of 99 SNe Ia is in clearly better agreement with a model with one class of SN Ia light curves and shows no evidence for distinct NUV sub-classes. The SDSS sample of 59 SNe Ia with poorer colour resolution does not distinguish between the two models.

Description: To better constrain the hypotheses proposed to explain why only a few quasars are radio loud (RL), we compare the characteristics of 1958 nearby ( z ≤ 0.3) SDSS (Sloan Digital Sky Survey) quasars, covered by the FIRST (Faint Images of the Radio Sky at Twenty-centimeters) and NVSS (NRAO VLA Sky Survey) radio surveys. Only 22 per cent are RL with log ( L 1.4 GHz ) ≥ 22.5 W Hz –1 , the majority being compact (C), weak radio sources (WRS), with log ( L 1.4 GHz ) 〈 24.5 W Hz –1 . 15 per cent of the RL quasars have extended radio morphologies: 3 per cent have a core and a jet (J), 2 per cent have a core with one lobe (L), and 10 per cent have a core with two lobes (T), the majority being powerful radio sources (PRS), with log ( L 1.4 GHz ) ≥ 24.5 W Hz –1 . In general, RL quasars have higher bolometric luminosities and ionization powers than radio-quiet (RQ) quasars. The WRS have comparable black hole (BH) masses as the RQ quasars, but higher accretion rates or radiative efficiencies. The PRS have higher BH masses than the WRS, but comparable accretion rates or radiative efficiencies. The WRS also have higher ${\rm FWHM}_{\rm [O\,\small {iii}]}$ than the PRS, consistent with a coupling of the spectral characteristics of the quasars with their radio morphologies. Inspecting the SDSS images and applying a neighbour search algorithm reveal no difference between the RQ and RL quasars of their host galaxies, environments, and interaction. Our results prompt the conjecture that the phenomenon that sparks the RL phase in quasars is transient, intrinsic to the active galactic nuclei, and stochastic, due to the chaotic nature of the accretion process of matter on to the BHs.

Description: We present the results of the first, deep Atacama Large Millimeter Array (ALMA) imaging covering the full ~=4.5 arcmin 2 of the Hubble Ultra Deep Field (HUDF) imaged with Wide Field Camera 3/IR on HST . Using a 45-pointing mosaic, we have obtained a homogeneous 1.3-mm image reaching 1.3 ~= 35 μJy, at a resolution of ~=0.7 arcsec. From an initial list of ~=50 〉 3.5 peaks, a rigorous analysis confirms 16 sources with S 1.3 〉 120 μJy. All of these have secure galaxy counterparts with robust redshifts (〈 z 〉 = 2.15). Due to the unparalleled supporting data, the physical properties of the ALMA sources are well constrained, including their stellar masses ( M * ) and UV+FIR star formation rates (SFR). Our results show that stellar mass is the best predictor of SFR in the high-redshift Universe; indeed at z ≥ 2 our ALMA sample contains seven of the nine galaxies in the HUDF with M * ≥ 2 x 10 10 M , and we detect only one galaxy at z 〉 3.5, reflecting the rapid drop-off of high-mass galaxies with increasing redshift. The detections, coupled with stacking, allow us to probe the redshift/mass distribution of the 1.3-mm background down to S 1.3 ~= 10 μJy. We find strong evidence for a steep star-forming ‘main sequence’ at z ~= 2, with SFR M * and a mean specific SFR ~= 2.2 Gyr –1 . Moreover, we find that ~=85 per cent of total star formation at z ~= 2 is enshrouded in dust, with ~=65 per cent of all star formation at this epoch occurring in high-mass galaxies ( M * 〉 2 x 10 10 M ), for which the average obscured:unobscured SF ratio is ~=200. Finally, we revisit the cosmic evolution of SFR density; we find this peaks at z ~= 2.5, and that the star-forming Universe transits from primarily unobscured to primarily obscured at z ~= 4.

Description: We introduce the concept of a class of equivalence of molecular clouds represented by an abstract spherically symmetric, isotropic object. This object is described by use of abstract scales in respect to a given mass-density distribution. Mass and average density are ascribed to each scale and thus are linked to the density distribution: a power-law type and an arbitrary continuous one. In the latter case, we derive a differential relationship between the mean density at a given scale and the structure parameter that defines the mass-density relationship. The two-dimensional (2D) projection of the cloud along the line of sight is also investigated. Scaling relations of mass and mean density are derived in the considered cases of power-law and arbitrary continuous distributions. We obtain relations between scaling exponents in the 2D and 3D cases. The proposed classes of equivalence are representative for the general structure of real clouds with various types of column-density distributions: power law, lognormal or combination of both.

Description: Determining neutron star (NS) radii and masses can help to understand the properties of matter at supra-nuclear densities. Thermal emission during thermonuclear X-ray bursts from NSs in low-mass X-ray binaries provides a unique opportunity to study NS parameters, because of the high fluxes, large luminosity variations and the related changes in the spectral properties. The standard cooling tail method uses hot NS atmosphere models to convert the observed spectral evolution during cooling stages of X-ray bursts to the Eddington flux F Edd and the stellar angular size . These are then translated to the constraints on the NS mass M and radius R . Here we present the improved, direct cooling tail method that generalizes the standard approach. First, we adjust the cooling tail method to account for the bolometric correction to the flux. Then, we fit the observed dependence of the blackbody normalization on flux with a theoretical model directly on the M – R plane by interpolating theoretical dependences to a given gravity, hence ensuring only weakly informative priors for M and R instead of F Edd and . The direct cooling method is demonstrated using a photospheric radius expansion burst from SAX J1810.8–2609, which has happened when the system was in the hard state. Comparing to the standard cooling tail method, the confidence regions are shifted by 1 towards larger radii, giving R  = 11.5–13.0 km at M  = 1.3–1.8 M for this NS.

Description: We present the CAlibrating LYMan-α with Hα (CALYMHA) pilot survey and new results on Lyman α (Lyα) selected galaxies at z  ~ 2. We use a custom-built Lyα narrow-band filter at the Isaac Newton Telescope, designed to provide a matched volume coverage to the z  = 2.23 Hα HiZELS survey. Here, we present the first results for the COSMOS and UDS fields. Our survey currently reaches a 3 line flux limit of ~4  x  10 –17  erg s –1  cm –2 , and a Lyα luminosity limit of ~10 42.3  erg s –1 . We find 188 Lyα emitters over 7.3  x  10 5  Mpc 3 , but also find significant numbers of other line-emitting sources corresponding to He ii , C iii ] and C iv emission lines. These sources are important contaminants, and we carefully remove them, unlike most previous studies. We find that the Lyα luminosity function at z  = 2.23 is very well described by a Schechter function up to L Ly α 10 43  erg s –1 with $L^{\ast }=10^{42.59^{+0.16}_{-0.08}}$  erg s –1 , $\phi ^{\ast }=10^{-3.09^{+0.14}_{-0.34}}$  Mpc –3 and α = –1.75 ± 0.25. Above L Ly α 10 43  erg s –1 , the Lyα luminosity function becomes power-law like, driven by X-ray AGN. We find that Lyα-selected emitters have a high escape fraction of 37 ± 7 per cent, anticorrelated with Lyα luminosity and correlated with Lyα equivalent width. Lyα emitters have ubiquitous large (40 kpc) Lyα haloes, ~2 times larger than their Hα extents. By directly comparing our Lyα and Hα luminosity functions, we find that the global/overall escape fraction of Lyα photons (within a 13 kpc radius) from the full population of star-forming galaxies is 5.1 ± 0.2 per cent at the peak of the star formation history. An extra 3.3 ± 0.3 per cent of Lyα photons likely still escape, but at larger radii.

Description: We compare five sub-grid models for supernova (SN) feedback in adaptive mesh refinement (AMR) simulations of isolated dwarf and L-star disc galaxies with 20–40 pc resolution. The models are thermal dump, stochastic thermal, ‘mechanical’ (injecting energy or momentum depending on the resolution), kinetic and delayed cooling feedback. We focus on the ability of each model to suppress star formation and generate outflows. Our highest resolution runs marginally resolve the adiabatic phase of the feedback events, which correspond to 40 SN explosions, and the first three models yield nearly identical results, possibly indicating that kinetic and delayed cooling feedback converge to wrong results. At lower resolution all models differ, with thermal dump feedback becoming inefficient. Thermal dump, stochastic and mechanical feedback generate multiphase outflows with mass loading factors β 〈〈 1, which is much lower than observed. For the case of stochastic feedback, we compare to published SPH simulations, and find much lower outflow rates. Kinetic feedback yields fast, hot outflows with β ~ 1, but only if the wind is in effect hydrodynamically decoupled from the disc using a large bubble radius. Delayed cooling generates cold, dense and slow winds with β 〉 1, but large amounts of gas occupy regions of temperature–density space with short cooling times. We conclude that either our resolution is too low to warrant physically motivated models for SN feedback, that feedback mechanisms other than SNe are important or that other aspects of galaxy evolution, such as star formation, require better treatment.

Description: We study the role of systematic effects in observational studies of the cusp–core problem under the minimum disc approximation using a suite of high-resolution (25-pc softening length) hydrodynamical simulations of dwarf galaxies. We mimic realistic kinematic observations and fit the mock rotation curves with two analytic models commonly used to differentiate cores from cusps in the dark matter distribution. We find that the cored pseudo-isothermal sphere (ISO) model is strongly favoured by the reduced $\chi ^2_\nu$ of the fits in spite of the fact that our simulations contain cuspy Navarro–Frenk–White profiles (NFW). We show that even idealized measurements of the gas circular motions can lead to the incorrect answer if velocity underestimates induced by pressure support, with a typical size of order ~5 km s –1 in the central kiloparsec, are neglected. Increasing the spatial resolution of the mock observations leads to more misleading results because the inner region, where the effect of pressure support is most significant, is better sampled. Fits to observations with a spatial resolution of 100 pc (2 arcsec at 10 Mpc) favour the ISO model in 78–90 per cent of the cases, while at 800-pc resolution, 41–77 per cent of the galaxies indicate the fictitious presence of a dark matter core. The coefficients of our best-fitting models agree well with those reported in observational studies; therefore, we conclude that NFW haloes cannot be ruled out reliably from this type of analysis.

Description: Galaxy formation models are now able to reproduce observed relations such as the relation between galaxies’ star formation rates (SFRs) and stellar masses ( M * ) and the stellar-mass–halo-mass relation. We demonstrate that comparisons of the short-time-scale variability in galaxy SFRs with observational data provide an additional useful constraint on the physics of galaxy formation feedback. We apply SFR indicators with different sensitivity time-scales to galaxies from the Feedback in Realistic Environments (FIRE) simulations. We find that the SFR– M * relation has a significantly greater scatter when the Hα-derived SFR is considered compared with when the far-ultraviolet (FUV)-based SFR is used. This difference is a direct consequence of bursty star formation because the FIRE galaxies exhibit order-of-magnitude SFR variations over time-scales of a few Myr. We show that the difference in the scatter between the simulated Hα- and FUV-derived SFR– M * relations at z  = 2 is consistent with observational constraints. We also find that the Hα/FUV ratios predicted by the simulations at z  = 0 are similar to those observed for local galaxies except for a population of low-mass ( M * 10 9.5 M ) simulated galaxies with lower Hα/FUV ratios than observed. We suggest that future cosmological simulations should compare the Hα/FUV ratios of their galaxies with observations to constrain the feedback models employed.

Description: We present photometric and high-dispersion spectroscopic measurements that show HR 7920 is a periodic variable. The photometry reveals at least four frequencies higher that 10 d –1 , two of which are also probably present in the radial velocity variations. The frequencies are in a range typical of Scuti star pulsations. A further low frequency of about 2.8 d –1 may be present in both radial velocities and photometry; if real, this points to Doradus variability, which would make HR 7920 a hybrid pulsator. An attempt is made to identify the modes of the Scuti pulsations, which include both radial and non-radial modes. A new rotational velocity of 75 km s –1 is derived from co-added spectra, contrasting with published values in the range 128–150 km s –1 .

Description: We perform smoothed particle hydrodynamics (SPH) simulations of an isolated galaxy with a new treatment for dust formation and destruction. To this aim, we treat dust and metal production self-consistently with star formation and supernova (SN) feedback. For dust, we consider a simplified model of grain size distribution by representing the entire range of grain sizes with large and small grains. We include dust production in stellar ejecta, dust destruction by SN shocks, grain growth by accretion and coagulation and grain disruption by shattering. We find that the assumption of fixed dust-to-metal mass ratio becomes no longer valid when the galaxy is older than 0.2 Gyr, at which point the grain growth by accretion starts to contribute to the non-linear rise of dust-to-gas ratio. As expected in our previous one-zone model, shattering triggers grain growth by accretion since it increases the total surface area of grains. Coagulation becomes significant when the galaxy age is greater than ~ 1 Gyr; at this epoch, the abundance of small grains becomes high enough to raise the coagulation rate of small grains. We further compare the radial profiles of dust-to-gas ratio $(\mathcal {D})$ and dust-to-metal ratio $(\mathcal {D}/Z$ , i.e. depletion) at various ages with observational data. We find that our simulations broadly reproduce the radial gradients of dust-to-gas ratio and depletion. In the early epoch ( 0.3 Gyr), the radial gradient of $\mathcal {D}$ follows the metallicity gradient with $\mathcal {D}/Z$ determined by the dust condensation efficiency in stellar ejecta, while the $\mathcal {D}$ gradient is steeper than the Z gradient at the later epochs because of grain growth by accretion. The framework developed in this paper is applicable to any SPH-based galaxy evolution simulations including cosmological ones.

Description: The gravitationally lensed galaxy A1689-zD1 is one of the most distant spectroscopically confirmed sources ( z = 7.5). It is the earliest known galaxy where the interstellar medium (ISM) has been detected; dust emission was detected with the Atacama Large Millimetre Array (ALMA). A1689-zD1 is also unusual among high-redshift dust emitters as it is a sub- L * galaxy and is therefore a good prospect for the detection of gaseous ISM in a more typical galaxy at this redshift. We observed A1689-zD1 with ALMA in bands 6 and 7 and with the Green Bank Telescope (GBT) in band Q . To study the structure of A1689-zD1, we map the mm-thermal dust emission and find two spatial components with sizes about 0.4 – 1.7 kpc (lensing-corrected). The rough spatial morphology is similar to what is observed in the near-infrared with HST and points to a perturbed dynamical state, perhaps indicative of a major merger or a disc in early formation. The ALMA photometry is used to constrain the far-infrared spectral energy distribution, yielding a dust temperature ( T dust ~ 35–45 K for β = 1.5 – 2). We do not detect the CO(3-2) line in the GBT data with a 95 per cent upper limit of 0.3 mJy observed. We find a slight excess emission in ALMA band 6 at 220.9 GHz. If this excess is real, it is likely due to emission from the [C ii ] 158.8 μm line at $z_{\rm [C\,\small {II}]} = 7.603$ . The stringent upper limits on the [C ii ] L FIR luminosity ratio suggest a [C ii ] deficit similar to several bright quasars and massive starbursts.

Description: In this paper, we study the triaxial properties of dark matter haloes of a wide range of masses extracted from a set of cosmological N -body simulations. We measure the shape at different distances from the halo centre (characterized by different overdensity thresholds), both in three and in two dimensions. We discuss how halo triaxiality increases with mass, redshift and distance from the halo centre. We also examine how the orientations of the different ellipsoids are aligned with each other and what is the gradient in internal shapes for haloes with different virial configurations. Our findings highlight that the internal part of the halo retains memory of the violent formation process keeping the major axis oriented towards the preferential direction of the infalling material while the outer part becomes rounder due to continuous isotropic merging events. This effect is clearly evident in high-mass haloes – which formed more recently – while it is more blurred in low-mass haloes. We present simple distributions that may be used as priors for various mass reconstruction algorithms, operating in different wavelengths, in order to recover a more complex and realistic dark matter distribution of isolated and relaxed systems.

Description: Circular polarization in cometary continuum bands has been observed for more than 30 years. Recently, imaging data on circular polarization have been obtained for more than 10 comets using the 6-m Big Telescope Alt-azimuthal (BTA) telescope (Russia). However, despite the accumulation of significant amounts of data, the mechanisms that form circular polarization in the cometary environment are still a mystery. Regular mechanisms, such as multiple scattering in an optically thick medium or the domination of particles or materials of a specific mirror asymmetry (including homochirality), could not explain the observations. Particle alignment was considered the most feasible mechanism; however, the cause of the particle alignment was not clear. The most reasonable mechanism, alignment in a magnetic field, was considered doubtful, as comets do not have their own magnetic field and, according to the in situ results for comet Halley, the solar magnetic field could not penetrate deeply into the coma. However, new theoretical studies of cometary coma interaction with the solar magnetic field and, especially, Rosetta observations of the diamagnetic cavity of comet 67P/Churyumov–Gerasimenko showed that the solar wind magnetic field can penetrate as close to the nucleus as several dozen kilometres. This allows us to suggest alignment in the solar magnetic field as a reason for the observed circular polarization. Based on the data obtained for comet 67P, we estimate the time necessary for the alignment of cometary particles in the solar magnetic field. The estimates obtained are consistent with the observations of cometary circular polarization.

Description: Centaur 174P/Echeclus, initially designated as (60558) 2000 EC 98 , presented three outbursts. A first and main one detected in 2005 December, another smaller one detected in 2011 May and a last one at the end of 2016 August. The first outburst was the largest one ever detected for a Centaur, of the order of 30 times that seen in other similar bodies. Because of the special interest of this target, and its brightness, we now have a large set of observational data were obtained before, during and after the two first outbursts. We present here new observational data obtained after the main outburst or coming from archives and an analysis of them. The main results of our study are (i) an absence of light curve in our 2013 data (while it was ~0.24 mag in the R -band in 2002–2003) and (ii) a satisfactory fit of the main outburst with two short events and a longer one (three sources of dust). Both results suggest a high obliquity of the rotation axis. We also discuss the origin of these outbursts and conclude that they are probably related to internal inhomogeneities of the nucleus.

Description: The length and pattern speed of the Milky Way bar are still controversial. Photometric and spectroscopic surveys of the inner Galaxy, as well as gas kinematics, favour a long and slowly rotating bar, with corotation around a Galactocentric radius of 6 kpc. On the other hand, the existence of the Hercules stream in local velocity space favours a short and fast bar with corotation around 4 kpc. This follows from the fact that the Hercules stream looks like a typical signature of the outer Lindblad resonance of the bar. As we showed recently, reconciling this local stream with a slow bar would need to find a yet unknown alternative explanation, based, for instance, on the effect of spiral arms. Here, by combining the TGAS catalogue of the Gaia DR1 with LAMOST radial velocities, we show that the position of Hercules in velocity space as a function of radius in the outer Galaxy indeed varies exactly as predicted by fast bar models with a pattern speed no less than 1.8 times the circular frequency at the Sun's position.

Description: In this paper, we present an analysis of the properties of blue straggler (BS) populations based on mocca simulations covering a range of initial globular cluster conditions. We broadly separate the BSs created in our simulations into two distinct types corresponding to their formation mechanism, namely evolutionary BSs formed from binary evolution and dynamical BSs formed from collisions or mergers induced by direct dynamical interactions between stars and binaries. We find that the dominant type of BS strongly depends on the initial semi-major axis distribution. With mostly compact binaries, the number of evolutionary BSs dominates. Conversely, with mostly wide binaries, dynamical BSs dominate. Higher cluster concentrations increase the contribution from dynamical BSs without affecting the numbers of evolutionary BSs, which are thus mostly descended from primordial binaries. We further consider the ratio between the number of BSs in binaries and as single stars ( R B/S ). Models that prefer compact and wide binaries begin with, respectively, high and low values of the ratio R B/S before converging to a nearly universal value ~ 0.4. Finally, the initial eccentricity distribution has little to no influence on BS formation.

Description: In the Milky Way there are thousands of stellar clusters each harbouring from a hundred to a million stars. Although clusters are common, the initial conditions of cluster formation are still not well understood. To determine the processes involved in the formation and evolution of clusters it is key to determine the global properties of cluster-forming clumps in their earliest stages of evolution. Here, we present the physical properties of 1244 clumps identified from the MALT90 survey. Using the dust temperature of the clumps as a proxy for evolution we determined how the clump properties change at different evolutionary stages. We find that less-evolved clumps exhibiting dust temperatures lower than 20 K have higher densities and are more gravitationally bound than more-evolved clumps with higher dust temperatures. We also identified a sample of clumps in a very early stage of evolution, thus potential candidates for high-mass star-forming clumps. Only one clump in our sample has physical properties consistent with a young massive cluster progenitor, reinforcing the fact that massive protoclusters are very rare in the Galaxy.

Description: The B-mode polarization power spectrum in the cosmic microwave background (CMB) is about four orders of magnitude fainter than the CMB temperature power spectrum. Any instrumental imperfections that couple temperature fluctuations to B-mode polarization must therefore be carefully controlled and/or removed. We investigate the role that a scan strategy can have in mitigating certain common systematics by averaging systematic errors down with many crossing angles. We present approximate analytic forms for the error on the recovered B-mode power spectrum that would result from differential gain, differential pointing and differential ellipticity for the case where two detector pairs are used in a polarization experiment. We use these analytic predictions to search the parameter space of common satellite scan strategies in order to identify those features of a scan strategy that have most impact in mitigating systematic effects. As an example, we go on to identify a scan strategy suitable for the CMB satellite proposed for the European Space Agency M5 call, considering the practical considerations of fuel requirement, data rate and the relative orientation of the telescope to the earth. Having chosen a scan strategy we then go on to investigate the suitability of the scan strategy.

Description: Data-driven model-independent reconstructions of the dark energy equation of state w ( z ) are presented using Planck 2015 era cosmic microwave background, baryonic acoustic oscillations (BAO), Type Ia supernova (SNIa) and Lyman α (Lyα) data. These reconstructions identify the w ( z ) behaviour supported by the data and show a bifurcation of the equation of state posterior in the range 1.5 〈  z  〈 3. Although the concordance cold dark matter (CDM) model is consistent with the data at all redshifts in one of the bifurcated spaces, in the other, a supernegative equation of state (also known as ‘phantom dark energy’) is identified within the 1.5 confidence intervals of the posterior distribution. To identify the power of different data sets in constraining the dark energy equation of state, we use a novel formulation of the Kullback–Leibler divergence. This formalism quantifies the information the data add when moving from priors to posteriors for each possible data set combination. The SNIa and BAO data sets are shown to provide much more constraining power in comparison to the Lyα data sets. Further, SNIa and BAO constrain most strongly around redshift range 0.1–0.5, whilst the Lyα data constrain weakly over a broader range. We do not attribute the supernegative favouring to any particular data set, and note that the CDM model was favoured at more than 2 log-units in Bayes factors over all the models tested despite the weakly preferred w ( z ) structure in the data.

Description: We studied active galactic nucleus (AGN) activity in 12 large-scale structures (LSSs) in the Observations of Redshift Evolution in Large-Scale Environments (ORELSE) survey, at 0.65 〈 z 〈 1.28, using a combination of Chandra observations, optical and NIR imaging and spectroscopy. We located a total of 61 AGNs that were successfully matched to optical counterparts in the LSSs. We found that AGN populations across our sample had more recently had starburst events compared to the overall galaxy populations. We find no relation between AGN activity and location within the LSSs, suggesting triggering mechanisms that depend on global environment are at most sub-dominant. To focus on differences between our AGNs, we grouped them into four sub-samples based on the spectral properties of their parents LSSs. We found one of the sub-samples, SG0023 & SC1604, stood out from the others. AGNs in this sample were disproportionately luminous. These AGNs had the most recent starburst events, in contrast to their parent populations. Additionally, both the AGNs and the overall galaxy population in SG0023 & SC1604 had the largest fraction of close kinematic pairs, which indicates a higher rate of galaxy mergers and interactions. These results suggest that major mergers are driving AGN activity in SG0023 & SC1604, while other processes are likely triggering less luminous AGNs in the rest of our sample. Additionally, minor mergers are unlikely to play a significant role, since the same conditions that lead to more major mergers should also lead to more minor mergers, which is not observed in SG0023 & SC1604.

Description: The evolutionary status of the chemically peculiar class of  Boo stars has been intensely debated. It is now agreed that the  Boo phenomenon affects A stars of all ages, from star formation to the terminal age main sequence, but the cause of the chemical peculiarity is still a puzzle. We revisit the debate of their ages and temperatures in order to shed light on the phenomenon, using the new parallaxes in Gaia Data Release 1 with existing Hipparcos parallaxes and multicolour photometry. We find that no single formation mechanism is able to explain all the observations, and suggest that there are multiple channels producing  Boo spectra. The relative importance of these channels varies with age, temperature and environment.

Description: We present a comprehensive UBVRI and Washington CT 1 T 2 photometric analysis of seven catalogued open clusters, namely: Ruprecht 3, 9, 37, 74, 150, ESO 324-15 and 436-2. The multiband photometric data sets in combination with 2MASS photometry and Gaia astrometry for the brighter stars were used to estimate their structural parameters and fundamental astrophysical properties. We found that Ruprecht 3 and ESO 436-2 do not show self-consistent evidence of being physical systems. The remained studied objects are open clusters of intermediate age (9.0 ≤ log( t  yr –1 ) ≤ 9.6), of relatively small size ( r cls  ~ 0.4–1.3 pc) and placed between 0.6 and 2.9 kpc from the Sun. We analysed the relationships between core, half-mass, tidal and Jacoby radii as well as half-mass relaxation times to conclude that the studied clusters are in an evolved dynamical stage. The total cluster masses obtained by summing those of the observed cluster stars resulted to be ~10–15 per cent of the masses of open clusters of similar age located closer than 2 kpc from the Sun. We found that cluster stars occupy volumes as large as those for tidally filled clusters.

Description: We present the chemical abundance analysis of 19 upper main-sequence stars of the young open cluster NGC 6250 (log t ~ 7.42 yr). This work is part of a project aimed at setting observational constraints on the theory of atomic diffusion in stellar photospheres, by means of a systematic study of the abundances of the chemical elements of early F-, A- and late B-type stars of well-determined age. Our data set consists of low-, medium- and high-resolution spectra obtained with the Fibre Large Array Multi Element Spectrograph (FLAMES) instrument of the ESO Very Large Telescope (VLT). To perform our analysis, we have developed a new suite of software tools for the chemical abundance analysis of stellar photospheres in local thermodynamical equilibrium. Together with the chemical composition of the stellar photospheres, we have provided new estimates of the cluster mean radial velocity, proper motion, refined the cluster membership, and we have given the stellar parameters including masses and fractional age. We find no evidence of statistically significant correlation between any of the parameters, including abundance and cluster age, except perhaps for an increase in Ba abundance with cluster age. We have proven that our new software tool may be successfully used for the chemical abundance analysis of large data sets of stellar spectra.

Description: NGC 1313 is a bulgeless nearby galaxy, classified as SB(s)d. Its proximity allows high spatial resolution observations. We performed the first detailed analysis of the emission-line properties in the nuclear region of NGC 1313, using an optical data cube obtained with the Gemini Multi-object Spectrograph. We detected four main emitting areas, three of them (regions 1, 2 and 3) having spectra typical of H ii regions. Region 1 is located very close to the stellar nucleus and shows broad spectral features characteristic of Wolf–Rayet stars. Our analysis revealed the presence of one or two WC4-5 stars in this region, which is compatible with results obtained by previous studies. Region 4 shows spectral features (as a strong Hα emission line, with a broad component) typical of a massive emission-line star, such as a luminous blue variable, a B[e] supergiant or a B hypergiant. The radial velocity map of the ionized gas shows a pattern consistent with rotation. A significant drop in the values of the gas velocity dispersion was detected very close to region 1, which suggests that the young stars there were formed from this cold gas, possibly keeping low values of velocity dispersion. Therefore, although detailed measurements of the stellar kinematics were not possible (due to the weak stellar absorption spectrum of this galaxy), we predict that NGC 1313 may also show a drop in the values of the stellar velocity dispersion in its nuclear region.

Description: We report a 20-yr campaign to track the 1.8 h photometric (and orbital) wave in the recurrent nova T Pyxidis. Before and after the 2011 eruption, the period increased on a time-scale P / $\dot{P}$ = 3 x 10 5 yr. This suggests a mass transfer rate in quiescence of ~10 –7 M yr –1 , in substantial agreement with the accretion rate based on the star's luminosity. During the eruption itself, a rapid period increase of 0.0054(7) per cent occurred. This is probably a measure of the mass ejected in the outburst. For a plausible choice of binary parameters, that mass is at least 3 x 10 –5 M , and probably more. This represents 〉300 yr of accretion at the pre-outburst rate, but the time between outbursts was only 45 yr. Thus, the erupting white dwarf (WD) seems to have ejected at least six times more mass than it accreted. If this eruption is typical, the WD must be eroding, rather than growing, in mass. Unless the present series of eruptions is a short-lived episode, the binary dynamics will evaporate the secondary in ~10 5 yr. This could be a major channel by which short-period cataclysmic variables are removed from the population.

Description: Tidal streams in the Milky Way are sensitive probes of the population of low-mass dark matter subhaloes predicted in cold dark matter (CDM) simulations. We present a new calculus for computing the effect of subhalo fly-bys on cold streams based on the action–angle representation of streams. The heart of this calculus is a line-of-parallel-angle approach that calculates the perturbed distribution function of a stream segment by undoing the effect of all relevant impacts. This approach allows one to compute the perturbed stream density and track in any coordinate system in minutes for realizations of the subhalo distribution down to 10 5 M , accounting for the stream's internal dispersion and overlapping impacts. We study the statistical properties of density and track fluctuations with large suites of simulations of the effect of subhalo fly-bys. The one-dimensional density and track power spectra along the stream trace the subhalo mass function, with higher mass subhaloes producing power only on large scales, while lower mass subhaloes cause structure on smaller scales. We also find significant density and track bispectra that are observationally accessible. We further demonstrate that different projections of the track all reflect the same pattern of perturbations, facilitating their observational measurement. We apply this formalism to data for the Pal 5 stream and make a first rigorous determination of $10^{+11}_{-6}$ dark matter subhaloes with masses between 10 6.5 and 10 9 M within 20 kpc from the Galactic centre [corresponding to $1.4^{+1.6}_{-0.9}$ times the number predicted by CDM-only simulations or to f sub ( r 〈 20 kpc) 0.2 per cent] assuming that the Pal 5 stream is 5 Gyr old. Improved data will allow measurements of the subhalo mass function down to 10 5 M , thus definitively testing whether dark matter is clumpy on the smallest scales relevant for galaxy formation.

Description: We evaluate the covariance matrix of the matter power spectrum using perturbation theory up to dominant terms at 1-loop order and compare it to numerical simulations. We decompose the covariance matrix into the disconnected (Gaussian) part, trispectrum from the modes outside the survey (supersample variance) and trispectrum from the modes inside the survey, and show how the different components contribute to the overall covariance matrix. We find the agreement with the simulations is at a 10 per cent level up to k  ~ 1 h Mpc –1 . We show that all the connected components are dominated by the large-scale modes ( k  〈 0.1 h Mpc –1 ), regardless of the value of the wave vectors k , k ' of the covariance matrix, suggesting that one must be careful in applying the jackknife or bootstrap methods to the covariance matrix. We perform an eigenmode decomposition of the connected part of the covariance matrix, showing that at higher k , it is dominated by a single eigenmode. The full covariance matrix can be approximated as the disconnected part only, with the connected part being treated as an external nuisance parameter with a known scale dependence, and a known prior on its variance for a given survey volume. Finally, we provide a prescription for how to evaluate the covariance matrix from small box simulations without the need to simulate large volumes.

Description: We investigate the transition of the turbulence from large to kinetic scales using Cluster observations. Simultaneous spectra of magnetic and electric fields in the Earth's magnetosheath from magnetohydrodynamic (MHD) to electron scales are presented for the first time. While the two spectra have approximatively similar behaviour in the fluid-MHD regime, they show different trends in the kinetic range. As the magnetic field spectrum steepens at ion scales, the electric field spectrum is characterized by a shallower power law continuing down to electron scales. Such an evolution is consistent with theoretical expectations, assuming that the turbulence is dominated by highly oblique ${\boldsymbol {k}}$ -vectors and that between ion and electron scales the electric field is governed by the non-ideal terms in the generalized Ohm's law. This leads to an expected linear increase of the electric-to-magnetic ratio of fluctuations, consistent with observations presented here. The influence of local whistler wave activity on electron-scale spectra is also discussed.

Description: We present the results of a six-year spectroscopic monitoring of DY Lyncis. Three different echelle spectrographs were used to collect the spectroscopic data. Each DY Lyncis spectrum contains lines of three different stars. Two of them belong to a very close eclipsing binary (EB) with an orbital period of 1.3 d. The reflex motion due to the third body can be observed in the radial velocities of the EB. We found the period of the wide orbit to be 281 d and its eccentricity is 0.33. We used the Wilson–Devinney method to fit both orbits. The analysis revealed that the EB consists of two very similar stars of 1.21 and 1.14 M , corresponding to a mass ratio of 0.94. The fit of the long-period orbit showed that the third body is the most massive component in the system, its mass is 1.40 M . Additionally, the atmospheric parameters were calculated for all three components. For that, we acquired spectra with a 2-m class telescope where we obtained sufficient signal-to-noise ratio. We derived temperatures of 6370 ± 150 and 6260 ± 140 K for the EB components, and 6380 ± 110 K for the most massive star. From the combined photometric and spectroscopic analysis, we estimate that the distance and age of the system are 285 pc and 2.5 Gyr, respectively.

Description: We present a catalogue of candidate Hα emission and absorption line sources and blue objects in the Galactic Bulge Survey (GBS) region. We use a point source catalogue of the GBS fields (two strips of (l  x  b) = (6°  x  1°) centred at b  = 1 $_{.}^{\circ}$ 5 above and below the Galactic Centre), covering the magnitude range 16 ≤ r ' ≤ 22.5. We utilize ( r '  –  i ' , r '  – Hα) colour–colour diagrams to select Hα emission and absorption line candidates, and also identify blue objects (compared to field stars) using the r '  –  i ' colour index. We identify 1337 Hα emission line candidates and 336 Hα absorption line candidates. These catalogues likely contain a plethora of sources, ranging from active (binary) stars, early-type emission line objects, cataclysmic variables (CVs) and low-mass X-ray binaries (LMXBs) to background active galactic nuclei (AGN). The 389 blue objects we identify are likely systems containing a compact object, such as CVs, planetary nebulae and LMXBs. Hot subluminous dwarfs (sdO/B stars) are also expected to be found as blue outliers. Cross-matching our outliers with the GBS X-ray catalogue yields 16 sources, including 7 (magnetic) CVs and 1 qLMXB candidate among the emission line candidates and 1 background AGN for the absorption line candidates. One of the blue outliers is a high-state AM CVn system. Spectroscopic observations combined with the multiwavelength coverage of this area, including X-ray, ultraviolet and (time-resolved) optical and infrared observations, can be used to further constrain the nature of individual sources.

Description: We have investigated the critical conditions required for a steady propeller effect for magnetized neutron stars with optically thick, geometrically thin accretion discs. We have shown through simple analytical calculations that a steady-state propeller mechanism cannot be sustained at an inner disc radius where the viscous and magnetic stresses are balanced. The radius calculated by equating these stresses is usually found to be close to the conventional Alfv $\acute{\mathrm{e}}$ n radius for spherical accretion, r A . Our results show that: (1) a steady propeller phase can be established with a maximum inner disc radius that is at least ~15 times smaller than r A depending on the mass-flow rate of the disc, rotational period and strength of the magnetic dipole field of the star, (2) the critical accretion rate corresponding to the accretion-propeller transition is orders of magnitude lower than the rate estimated by equating r A to the co-rotation radius. Our results are consistent with the properties of the transitional millisecond pulsars that show transitions between the accretion powered X-ray pulsar and the rotational powered radio-pulsar states.

Description: Supernova (SN) 2008bk is a well-observed low-luminosity Type II event visually associated with a low-mass red-supergiant progenitor. To model SN 2008bk, we evolve a 12 M star from the main sequence until core collapse, when it has a total mass of 9.88 M , a He-core mass of 3.22 M and a radius of 502 R . We then artificially trigger an explosion that produces 8.29 M of ejecta with a total energy of 2.5  x  10 50  erg and ~0.009 M of 56 Ni. We model the subsequent evolution of the ejecta with non-local thermodynamic equilibrium time-dependent radiative transfer. Although somewhat too luminous and energetic, this model reproduces satisfactorily the multiband light curves and multi-epoch spectra of SN 2008bk, confirming the suitability of a low-mass massive star progenitor. As in other low-luminosity SNe II, the structured Hα profile at the end of the plateau phase is probably caused by Ba  ii  6496.9 Å rather than asphericity. We discuss the sensitivity of our results to changes in progenitor radius and mass, as well as chemical mixing. A 15 per cent increase in progenitor radius causes a 15 per cent increase in luminosity and a 0.2 mag V -band brightening of the plateau but leaves its length unaffected. An increase in ejecta mass by 10 per cent lengthens the plateau by ~10 d. Chemical mixing introduces slight changes to the bolometric light curve, limited to the end of the plateau, but has a large impact on colours and spectra at nebular times.

Description: High critical density molecular lines like HCN (1-0) or HCO + (1-0) represent our best tool to study currently star-forming, dense molecular gas at extragalactic distances. The optical depth of these lines is a key ingredient to estimate the effective density required to excite emission. However, constraints on this quantity are even scarcer in the literature than measurements of the high-density tracers themselves. Here, we combine new observations of HCN, HCO + and HNC (1-0) and their optically thin isotopologues H 13 CN, H 13 CO + and HN 13 C (1-0) to measure isotopologue line ratios. We use IRAM 30-m observations from the large programme EMPIRE and new Atacama Large Millimetre/submillimetre Array observations, which together target six nearby star-forming galaxies. Using spectral stacking techniques, we calculate or place strong upper limits on the HCN/H 13 CN, HCO + /H 13 CO + and HNC/HN 13 C line ratios in the inner parts of these galaxies. Under simple assumptions, we use these to estimate the optical depths of HCN (1-0) and HCO + (1-0) to be ~ 2–11 in the active, inner regions of our targets. The critical densities are consequently lowered to values between 5 and 20 x 10 5  cm –3 , 1 and 3 x 10 5  cm –3 and 9 x 10 4  cm –3 for HCN, HCO + and HNC, respectively. We study the impact of having different beam-filling factors, , on these estimates and find that the effective critical densities decrease by a factor of $\frac{\eta _{12}}{\eta _{13}}\,\tau _{12}$ . A comparison to existing work in NGC 5194 and NGC 253 shows the HCN/H 13 CN and HCO + /H 13 CO + ratios in agreement with our measurements within the uncertainties. The same is true for studies in other environments such as the Galactic Centre or nuclear regions of active galactic nucleus dominated nearby galaxies.

Description: We construct a sample of 9380 contact binaries (W UMa systems) by using the Catalina Real-Time Transient Survey Variables Sources Catalogue. By measuring brightness change rates, light-curve statistics, and temperatures for this sample, we improve the understanding of contact binary light-curve characteristics, and luminosity variability on decadal time-scales. We show that binaries with convective outer envelopes have a different distribution of light-curve amplitudes and magnitude differences between eclipse minima than binaries with radiative outer envelopes. We find that more than 2000 binaries exhibit a linear change in mean brightness over the 8-yr timespan of observations with at least 3 significance. We note that 25.9 per cent of binaries with convective outer envelopes exhibit a significant change in brightness, while only 10.5 per cent of radiative binaries exhibit a significant change in brightness. In 205 binaries (2.2 per cent), we find that a sinusoid model better describes the luminosity trend within the 8-yr observation timespan. For these binaries, we report the amplitudes and periods (as estimated using observed half-periods) of this sinusoidal brightness variation and discuss possible mechanisms driving the variation.

Description: The recent discovery of an earth-like planet around Proxima Centauri has drawn much attention to this star and its environment. We performed a series of observations of Proxima Centauri using Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE), the planet-finder instrument installed at the European Southern Observatory (ESO) Very Large Telescope (VLT) UT3, using its near-infrared modules, InfraRed Dual-band Imager and Spectrograph (IRDIS) and IFS. No planet was detected directly, but we set upper limits on the mass up to 7 au by exploiting the AMES-COND models. Our IFS observations reveal that no planet more massive than ~6–7  M Jup can be present within 1 au. The dual-band imaging camera IRDIS also enables us to probe larger separations than other techniques such as radial velocity or astrometry. We obtained mass limits of the order of 4  M Jup at separations of 2 au or larger, representing the most stringent mass limits at separations larger than 5 au available at the moment. We also made an attempt to estimate the radius of possible planets around Proxima using the reflected light. Since the residual noise for the observations is dominated by photon noise and thermal background, longer exposures in good observing conditions could improve the achievable contrast limit further.

Description: We present new measurements of the power spectra of the cosmic infrared background (CIB) anisotropies using the Planck 2015 full-mission High frequency instrument data at 353, 545 and 857 GHz over 20 000 deg 2 . We use techniques similar to those applied for the cosmological analysis of Planck , subtracting dust emission at the power spectrum level. Our analysis gives stable solutions for the CIB power spectra with increasing sky coverage up to about 50 per cent of the sky. These spectra agree well with H i -cleaned spectra from Planck measured on much smaller areas of sky with low Galactic dust emission. At 545 and 857 GHz, our CIB spectra agree well with those measured from Herschel data. We find that the CIB spectra at 500 are well fitted by a power-law model for the clustered CIB, with a shallow index cib  = 0.53 ± 0.02. This is consistent with the CIB results at 217 GHz from the cosmological parameter analysis of Planck . We show that a linear combination of the 545 and 857 GHz Planck maps is dominated by the CIB fluctuations at multipoles 300.

Description: We develop two algorithms, based on maximum likelihood inference, for estimating the parameters of polarized radio sources which emit at a single rotation measure (RM), e.g. pulsars. These algorithms incorporate the flux density spectrum of the source, either a power law or a scaled version of the Stokes I spectrum, and a variation in sensitivity across the observing band. We quantify the detection significance and measurement uncertainties in the fitted parameters, and we derive weighted versions of the RM synthesis algorithm which, under certain conditions, maximize the likelihood. We use Monte Carlo simulations to compare injected and recovered source parameters for a range of signal-to-noise ratios, investigate the quality of standard methods for estimating measurement uncertainties and search for statistical biases. These simulations consider one frequency band each for the Australia Telescope Compact Array, the Square Kilometre Array (SKA) and the Low Frequency Array. We find that results obtained for one frequency band cannot be easily generalized, and that methods that were developed in the past for correcting bias in individual frequency channels do not apply to wide-band data sets. The standard method for estimating the measurement uncertainty in RM is not accurate for sources with non-zero spectral indices. Furthermore, dividing Stokes Q and U by Stokes I to correct for spectral index effects, in combination with RM synthesis, does not maximize the likelihood.

Description: A fundamental aspect of the three-body problem is its stability. Most stability studies have focused on the co-planar three-body problem, deriving analytic criteria for the dynamical stability of such pro/retrograde systems. Numerical studies of inclined systems phenomenologically mapped their stability regions, but neither complement it by theoretical framework, nor provided satisfactory fit for their dependence on mutual inclinations. Here we present a novel approach to study the stability of hierarchical three-body systems at arbitrary inclinations, which accounts not only for the instantaneous stability of such systems, but also for the secular stability and evolution through Lidov–Kozai cycles and evection. We generalize the Hill-stability criteria to arbitrarily inclined triple systems, explain the existence of quasi-stable regimes and characterize the inclination dependence of their stability. We complement the analytic treatment with an extensive numerical study, to test our analytic results. We find excellent correspondence up to high inclinations (~120°), beyond which the agreement is marginal. At such high inclinations, the stability radius is larger, the ratio between the outer and inner periods becomes comparable and our secular averaging approach is no longer strictly valid. We therefore combine our analytic results with polynomial fits to the numerical results to obtain a generalized stability formula for triple systems at arbitrary inclinations. Besides providing a generalized secular-based physical explanation for the stability of non-co-planar systems, our results have direct implications for any triple systems and, in particular, binary planets and moon/satellite systems; we briefly discuss the latter as a test case for our models.

Description: Hydrodynamical simulations of star formation often do not possess the dynamic range needed to fully resolve the build-up of individual stars and star clusters, and thus have to resort to sub-grid models. A popular way to do this is by introducing Lagrangian sink particles, which replace contracting high-density regions at the point where the resolution limit is reached. A common problem then is how to assign fundamental stellar properties to sink particles, such as the distribution of stellar masses. We present a new and simple statistical method to assign stellar contents to sink particles. Once the stellar content is specified, it can be used to determine a sink particle's radiative output, supernovae rate or other feedback parameters that may be required in the calculations. Advantages of our method are: (i) it is simple to implement; (ii) it guarantees that the obtained stellar populations are good samples of the initial mass function; (iii) it can easily deal with infalling mass accreted at later times; and (iv) it does not put restrictions on the sink particles’ masses in order to be used. The method works very well for sink particles that represent large star clusters and for which the stellar mass function is well sampled, but can also handle the transition to sink particles that represent a small number of stars.

Description: A simple model of a periodic ensemble of closely packed flux tubes, sitting atop a vertically stratified layer, reveals that an incident fast wave from below preferentially converts almost immediately to Alfvén waves in the flux tubes, with kink waves restricted to at most a very few Fourier modes. This suggests that observations of coronal kink modes in such structured systems may greatly underestimate the net wave-energy flux being transported into and through the corona, much of which may reside in harder-to-observe Alfvén waves. The processes of mode conversion/resonant absorption and Alfvén phase mixing are implicated. It is suggested that the Sun's internal p-mode field – the 5-min oscillations – may contribute substantially to the process by supplying incident fast waves in the chromosphere that scatter and mode-convert in the tube ensemble.

Description: We report the discovery of eight new giant planets, and updated orbits for four known planets, orbiting dwarf and subgiant stars using the CORALIE, HARPS, and MIKE instruments as part of the Calan–Hertfordshire Extrasolar Planet Search. The planets have masses in the range 1.1–5.4  M J 's, orbital periods from 40 to 2900 d, and eccentricities from 0.0 to 0.6. They include a double-planet system orbiting the most massive star in our sample (HD147873), two eccentric giant planets (HD128356 b and HD154672 b ), and a rare 14 Herculis analogue (HD224538 b ). We highlight some population correlations from the sample of radial velocity detected planets orbiting nearby stars, including the mass function exponential distribution, confirmation of the growing body of evidence that low-mass planets tend to be found orbiting more metal-poor stars than giant planets, and a possible period–metallicity correlation for planets with masses 〉0.1 M J , based on a metallicity difference of 0.16 dex between the population of planets with orbital periods less than 100 d and those with orbital periods greater than 100 d.

Description: One of the main goals of the feasibility study MOSE (MOdelling ESO Sites) is to evaluate the performances of a method conceived to forecast the optical turbulence (OT) above the European Southern Observatory (ESO) sites of the Very Large Telescope (VLT) and the European Extremely Large Telescope (E-ELT) in Chile. The method implied the use of a dedicated code conceived for the OT called astro-meso-nh . In this paper, we present results we obtained at conclusion of this project concerning the performances of this method in forecasting the most relevant parameters related to the OT ( $C_{N}^2$ , seeing , isoplanatic angle 0 and wavefront coherence time 0 ). Numerical predictions related to a very rich statistical sample of nights uniformly distributed along a solar year and belonging to different years have been compared to observations, and different statistical operators have been analysed such as the classical bias, root-mean-squared error, and more sophisticated statistical operators derived by the contingency tables that are able to quantify the score of success of a predictive method such as the percentage of correct detection (PC) and the probability to detect a parameter within a specific range of values (POD). The main conclusions of the study tell us that the astro-meso-nh model provides performances that are already very good to definitely guarantee a not negligible positive impact on the service mode of top-class telescopes and ELTs. A demonstrator for an automatic and operational version of the astro-meso-nh model will be soon implemented on the sites of VLT and E-ELT.

Description: We present a pilot study on the nearby massive barred galaxy NGC 1291, in which we use dynamical modelling to constrain the disc mass-to-light ratio ( M / L ), thus breaking the degeneracy between the baryonic and dark matter in its central regions. We use the gas, specifically the morphology of the dust lanes on the leading side of the bar, as a tracer of the underlying gravitational potential. We run a large number of hydrodynamic gas response simulations, in potentials obtained directly from near-infrared images of the galaxy, which have three free parameters: the M / L , the bar pattern speed and the height function. We explore the three-dimensional parameter space, by comparing the morphology of the shocks created in the gas response simulations with those of the observed dust lanes, and find the best-fitting models; these suggest that the M / L of NGC 1291 agrees with that predicted by stellar population synthesis models in the near-infrared (0.6 M /L ), which leads to a borderline maximum disc for this galaxy. Furthermore, we find that the bar rotates fast, with a corotation radius that is ≤1.4 times the bar length.

Description: We report on the redshift of the BL Lac object 3FGL J0909.0+2310 based on observations obtained with the OSIRIS Multi-Object Spectrograph (MOS) mounted on the 10.4-m Gran Telescopio Canarias. A redshift of 0.432 ± 0.002 was obtained by the identification of three absorption features (Ca ii K&H and the G band) detected in the spectrum of the BL Lac host galaxy. The closest object to the BL Lac at an angular separation of 3.8 arcsec (~21 kpc at this distance) has a similar redshift of 0.431 ± 0.002. This companion galaxy could be the most likely cause of the nuclear activity as postulated by studies based on more extended data sets and cosmological models. MOS allows us to study the object's neighbourhood within a field of view of approximately 7  x  2 arcmin 2 and we find two small groups of galaxies at redshifts 0.28 and 0.39 which are probably not related to the activity of 3FGL J0909.0+2310.

Description: We have used the XSHOOTER echelle spectrograph on the European Southern Obseratory (ESO) Very Large Telescope (VLT) to obtain UVB–VIS–NIR (ultraviolet–blue (UVB), visible (VIS) and near-infrared (NIR)) reflectance spectra of two members of the Eureka family of L5 Mars Trojans, in order to test a genetic relationship to Eureka. In addition to obtaining spectra, we also carried out VRI photometry of one of the VLT targets using the 2-m telescope at the Bulgarian National Astronomical Observatory – Rozhen and the two-channel focal reducer. We found that these asteroids belong to the olivine-dominated A, or S a , taxonomic class. As Eureka itself is also an olivine-dominated asteroid, it is likely that all family asteroids share a common origin and composition. We discuss the significance of these results in terms of the origin of the martian Trojan population.

Description: We performed a global study on the timing and spectral properties of type-B quasi-periodic oscillations (QPOs) in the outbursts of black hole X-ray binaries. The sample is built based on the observations of Rossi X-ray Timing Explorer ( RXTE ), via searching in the literature in RXTE era for all the identified type-B QPOs. To enlarge the sample, we also investigated some type-B QPOs that are reported but not yet fully identified. Regarding to the time lag and hard/soft flux ratio, we found that the sources with type-B QPOs behave in two subgroups. In one subgroup, type-B QPO shows a hard time lag that first decreases and then reverse into a soft time lag along with softening of the energy spectrum. In the other subgroup, type-B QPOs distribute only in a small region with hard time lag and relatively soft hardness. These findings may be understood with a diversity of the homogeneity showing up for the hot inner flow of different sources. We confirm the universality of a positive relation between the type-B QPO frequency and the hard component luminosity in different sources. We explain the results by considering that the type-B QPO photons are produced in the inner accretion flow around the central black hole, under a local Eddington limit. Using this relationship, we derived a mass estimation of 9.3–27.1 M for the black hole in H 1743–322.

Description: DDO 68 (UGC 5340) is an unusual dwarf galaxy with extremely low gas metallicity [12 + log (O/H) = 7.14] residing in the nearby Lynx–Cancer void. Despite its apparent isolation, it shows both optical and H i morphological evidence for strong tidal disturbance. Here, we study the resolved stellar populations of DDO 68 using deep images from the HST archive. We determined a distance of 12.75 ± 0.41 Mpc using the tip of the red giant branch (TRGB). The star formation history reconstruction reveals that about 60 per cent of stars formed during the initial period of star formation, about 12–14 Gyr ago. During the next 10 Gyr, DDO 68 was in the quenched state, with only slight traces of star formation. The onset of the most recent burst of star formation occurred about 300 Myr ago. We find that young populations with ages of several million to a few hundred million years are widely spread across various parts of DDO 68, indicating an intense star formation episode with a high mean rate of 0.15 M  yr –1 . A major fraction of the visible stars in the whole system (~80 per cent) have low metallicities: Z  = Z /50–Z /20. The properties of the northern periphery of DDO 68 can be explained by an ongoing burst of star formation induced by the minor merger of a small, gas-rich, extremely metal-poor galaxy with a more typical dwarf galaxy. The current TRGB-based distance of DDO 68 implies a total negative peculiar velocity of 500 km s –1 .

Description: We report an early science discovery of the 12 CO(1–0) emission line in the collisional ring galaxy VII Zw466, using the Redshift Search Receiver instrument on the Large Millimeter Telescope Alfonso Serrano. The apparent molecular-to-atomic gas ratio either places the interstellar medium (ISM) of VII Zw466 in the H i -dominated regime or implies a large quantity of CO-dark molecular gas, given its high star formation rate. The molecular gas densities and star formation rate densities of VII Zw466 are consistent with the standard Kennicutt–Schmidt star formation law even though we find this galaxy to be H 2 -deficient. The choice of CO-to- H 2 conversion factors cannot explain the apparent H 2 deficiency in its entirety. Hence, we find that the collisional ring galaxy, VII Zw466, is either largely deficient in both H 2 and H i or contains a large mass of CO-dark gas. A low molecular gas fraction could be due to the enhancement of feedback processes from previous episodes of star formation as a result of the star-forming ISM being confined to the ring. We conclude that collisional ring galaxy formation is an extreme form of galaxy interaction that triggers a strong galactic-wide burst of star formation that may provide immediate negative feedback towards subsequent episodes of star formation – resulting in a short-lived star formation history or, at least, the appearance of a molecular gas deficit.

Description: Line-of-sight integrals of the squared density, commonly called the J-factor , are essential for inferring dark matter (DM) annihilation signals. The J-factors of DM-dominated dwarf spheroidal satellite galaxies (dSphs) have typically been derived using Bayesian techniques, which for small data samples implies that a choice of priors constitutes a non-negligible systematic uncertainty. Here we report the development of a new fully frequentist approach to construct the profile likelihood of the J-factor. Using stellar kinematic data from several classical and ultra-faint dSphs, we derive the maximum likelihood value for the J-factor and its confidence intervals. We validate this method, in particular its bias and coverage, using simulated data from the Gaia Challenge . We find that the method possesses good statistical properties. The J-factors and their uncertainties are generally in good agreement with the Bayesian-derived values, with the largest deviations restricted to the systems with the smallest kinematic data sets. We discuss improvements, extensions, and future applications of this technique.