ALBERT

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

Description: At low redshifts, dust-obscured quasars often have strong yet narrow permitted lines in the rest-frame optical and ultraviolet, excited by the central active nucleus, earning the designation type II quasars. We present a sample of 145 candidate type II quasars at redshifts between 2 and 4.3, encompassing the epoch at which quasar activity peaked in the universe. These objects, selected from the quasar sample of the Baryon Oscillation Spectroscopic Survey of the Sloan Digital Sky Survey III, are characterized by weak continuum in the rest-frame ultraviolet (typical continuum magnitude of i 22) and strong lines of C iv and Lyα, with full width at half-maximum less than 2000 km s –1 . The continuum magnitudes correspond to an absolute magnitude of –23 or brighter at redshift 3, too bright to be due exclusively to the host galaxies of these objects. Roughly one third of the objects are detected in the shorter wavelength bands of the Wide-Field Infrared Survey Explorer survey; the spectral energy distributions of these objects appear to be intermediate between classic type I and type II quasars seen at lower redshift. Five objects are detected at rest frame 6 μm by Spitzer , implying bolometric luminosities of several times 10 46 erg s –1 . We have obtained polarization measurements for two objects; they are roughly 3 per cent polarized. We suggest that these objects are luminous quasars, with modest dust extinction ( A V  ~ 0.5 mag), whose ultraviolet continuum also includes a substantial scattering contribution. Alternatively, the line of sight to the central engines of these objects may be obscured by optically thick material whose covering fraction is less than unity.

Description: We calculate stellar masses for ~400 000 massive luminous galaxies at redshift ~0.2–0.7 using the first two years of data from the Baryon Oscillation Spectroscopic Survey (BOSS). Stellar masses are obtained by fitting model spectral energy distributions to u , g , r , i , z magnitudes, and simulations with mock galaxies are used to understand how well the templates recover the stellar mass. Accurate BOSS spectroscopic redshifts are used to constrain the fits. We find that the distribution of stellar masses in BOSS is narrow (log M  ~ 0.5 dex) and peaks at about log M/M  ~ 11.3 (for a Kroupa initial stellar mass function), and that the mass sampling is uniform over the redshift range 0.2–0.6, in agreement with the intended BOSS target selection. The galaxy masses probed by BOSS extend over ~10 12 M , providing unprecedented measurements of the high-mass end of the galaxy mass function. We find that the galaxy number density above ~2.5 10 11 M agrees with previous determinations. We perform a comparison with semi-analytic galaxy formation models tailored to the BOSS target selection and volume, in order to contain incompleteness. The abundance of massive galaxies in the models compare fairly well with the BOSS data, but the models lack galaxies at the massive end. Moreover, no evolution with redshift is detected from ~0.6 to 0.4 in the data, whereas the abundance of massive galaxies in the models increases to redshift zero. Additionally, BOSS data display colour–magnitude (mass) relations similar to those found in the local Universe, where the most massive galaxies are the reddest. On the other hand, the model colours do not display a dependence on stellar mass, span a narrower range and are typically bluer than the observations. We argue that the lack of a colour–mass relation for massive galaxies in the models is mostly due to metallicity, which is too low in the models.

Description: We have improved upon our previous search technique of systematically searching quasi-stellar object (QSO) spectra for narrow galactic Hα emission, which indicates a foreground galaxy within the Sloan Digital Sky Survey (SDSS) spectral fibre. We now search for Hα plus eight other galactic emission lines in the same manner. We have scanned the SDSS data release 7 (DR7) QSO catalogue spectra searching for these emission lines. Here, we present our sample which focuses on the redshift range z  〈 0.401 where galactic Hα is detectable in the SDSS spectra. This has revealed 27 unique galaxies on top of QSOs (GOTOQs). We have deblended the QSOs from the respective galaxies and determined the photometric properties of these systems. We find upon deblending that most of the galaxies are primarily blue, late-type galaxies with colours in the range –0.71 〈 ( u  –  r ) 〈 2.07. We find a slight anticorrelation between reddening and impact parameter [ E ( B  –  V ) ( g  –  i ) versus b ]. The galaxies have average star formation rates of 0.01–1 M  yr –1 , with an average of 0.6 M  yr –1 . They range in z from 0 to 0.4 and in stellar luminosity from about 0.01 L * to 3.0 L *. They are foreground to QSOs of brightness 17.4–20.4 mag ( r band) with the impact parameters of 1–10 kpc. They represent a fair sample of typical galaxies for which it should be possible to determine accurately various quantities (e.g. abundances, dust extinction and Faraday rotation) using follow-up analysis of the background QSOs. Where present, Ca ii 3934 (K) and Na i 5892 (D2) absorption lines were also measured in the QSO spectrum. We find 15 systems with Ca ii K absorption and 6 with Na i D2 absorption. We find no trends relating the equivalent widths of these lines to impact parameter or reddening of the background QSO. Eight of our fields show significant reddening [ E ( B  –  V ) ( g  –  i )  〉 0.20], which are targeted for follow-up studies of interstellar clouds. We find three systems (Q0059–0009, Q1033+2059 and Q2356+0029) with detectable galactic spectral emission, but no visible galaxy in imaging and no detectable absorption features. We speculate on the nature of these galaxies, which are strong candidates for dark galaxies and dwarf haloes.

Description: We present Hubble Space Telescope Cosmic Origins Spectrograph spectra of 10 quasars located behind M31, selected to investigate the properties of gas associated with its extended disc and high-velocity clouds (HVCs). The sightlines have impact parameters ranging between b  = 13 and 112 kpc. No absorption is detected in the four sightlines selected to sample any extended disc (or halo) gas that might be present in the outer regions of M31 beyond an impact parameter of b  〉 57 kpc. Of the six remaining sightlines, all of which lie at b 〈 32 kpc and within the N HI = 2 x 10 18  cm –2 boundary of the H i disc of M31, we detect low-ionization absorption at M31 velocities along four of them (three of which include Mg ii absorption). We also detect Mg ii absorption from an HVC. This HVC sightline does not pass through the 21 cm disc of M31, but we detect additional Mg ii absorption at velocities distinct from the HVC that presumably arises in the halo. We find that along sightlines where both are detected, the velocity location of the low-ion gas tracks the peak in 21 cm emission. High-ionization absorption is detected along the three inner sightlines, but not along the three outer sightlines, for which C iv data exist. As inferred from high-resolution 21 cm emission-line maps of M31's disc and extended regions, only one of the sightlines may be capable of harbouring a damped Lyα system, i.e. with N HI ≥ 2 x 10 20  cm –2 . This sightline has impact parameter b  = 17.5 kpc, and we detect both low- and high-ion absorption lines associated with it. The impact parameters of our observed sightlines through M31 are similar to the impact parameters of galaxies identified with Mg ii absorbers at redshifts 0.1 〈 z 〈 1.0 in a 2011 study by Rao et al. However, even if we only count cases where absorption due to M31 is detected, the Mg ii 2796 rest equivalent width values are significantly smaller. In comparison, moderate-to-strong Mg ii absorption from Milky Way gas is detected along all 10 sightlines. Thus, this study indicates that M31 does not present itself as an absorbing galaxy which is typical of higher-redshift galaxies inferred to give rise to moderate-strength quasar absorption lines. M31 also appears not to possess an extensive large gaseous cross-section, at least not along the direction of its major axis.

Description: We measure the sum of the neutrino particle masses using the three-dimensional galaxy power spectrum of the Sloan Digital Sky Survey III (SDSS-III) Baryon Oscillation Spectroscopic Survey Data Release 9 the constant MASS (CMASS) galaxy sample. Combined with the cosmic microwave background, supernova and additional baryonic acoustic oscillation data, we find upper 95 per cent confidence limits (CL) of the neutrino mass m  〈 0.340 eV within a flat cold dark matter (CDM) background, and m  〈 0.821 eV, assuming a more general background cosmological model. The number of neutrino species is measured to be N eff  = 4.308 ± 0.794 and $4.032^{+0.870}_{-0.894}$ for these two cases, respectively. We study and quantify the effect of several factors on the neutrino measurements, including the galaxy power spectrum bias model, the effect of redshift-space distortion, the cut-off scale of the power spectrum and the choice of additional data. The impact of neutrinos with unknown masses on other cosmological parameter measurements is investigated. The fractional matter density and the Hubble parameter are measured to be $\Omega _{\rm M}=0.2796\pm 0.0097,\ H_0=69.72^{+0.90}_{-0.91}$ km s –1  Mpc –1 (flat CDM) and $\Omega _{\rm M}=0.2798^{+0.0132}_{-0.0136}, H_0=73.78^{+3.16}_{-3.17}$ km s –1  Mpc –1 (more general background model). Based on a Chevallier–Polarski–Linder parametrization of the equation-of-state w of dark energy, we find that w  = –1 is consistent with observations, even allowing for neutrinos. Similarly, the curvature K and the running of the spectral index α s are both consistent with zero. The tensor-to-scalar ratio is constrained down to r  〈 0.198 (95 per cent CL, flat CDM) and r  〈 0.440 (95 per cent CL, more general background model).

Description: The circumgalactic medium (CGM) of typical galaxies is crucial to our understanding of the cycling of gas into, through and out of galaxies. One way to probe the CGM is to study gas around galaxies detected via the absorption lines they produce in the spectra of background quasars. Here, we present medium resolution and new ~0.4-arcsec resolution (~3 kpc at z  ~ 1) 3D observations with Very Large Telescope/Spectrograph for Integral Field Observations in the Near Infrared of galaxies responsible for high- N (H i ) quasar absorbers. These data allow us to determine in details the kinematics of the objects: the four z  ~ 1 objects are found to be rotation supported as expected from inclined discs, while the fifth z  ~ 2 system is dispersion dominated. Two of the systems show sign of interactions and merging. In addition, we use several indicators (star formation per unit area, a comparison of emission and absorption kinematics, arguments based on the inclination and the orientation of the absorber to the quasar line of sight and the distribution of metals) to determine the direction of the gas flows in and out of these galaxies. In some cases, our observations are consistent with the gas seen in absorption being due to material corotating with their haloes. In the case of absorbing galaxies towards Q1009–0026 and Q2222–0946, these indicators point towards the presence of an outflow traced in absorption.

Description: We present composite spectra constructed from a sample of 242 150 Lyman α (Lyα) forest absorbers at redshifts 2.4 〈 z 〈 3.1 identified in quasar spectra from the Baryon Oscillation Spectroscopic Survey (BOSS) as part of Data Release 9 of the Sloan Digital Sky Survey III. We select forest absorbers by their flux in bins 138 km s –1 wide (approximately the size of the BOSS resolution element). We split these absorbers into five samples spanning the range of flux –0.05 ≤ F 〈 0.45. Tests on a smaller set of high-resolution spectra show that our three strongest absorption samples would probe circumgalactic regions (projected separation 〈300 proper kpc and | v | 〈 300 km s –1 ) in about 60 per cent of cases for very high signal-to-noise ratio. Within this subset, weakening Lyα absorption is associated with decreasing purity of circumgalactic selection once BOSS noise is included. Our weaker two Lyα absorption samples are dominated by the intergalactic medium. We present composite spectra of these samples and a catalogue of measured absorption features from H  i and 13 metal ionization species, all of which we make available to the community. We compare measurements of seven Lyman series transitions in our composite spectra to single line models and obtain further constraints from their associated excess Lyman limit opacity. This analysis provides results consistent with column densities over the range $14.4 \lesssim \log (N_{\rm H\,\small {I}}) \lesssim 16.45$ . We compare our measurements of metal absorption to a variety of simple single-line, single-phase models for a preliminary interpretation. Our results imply clumping on scales down to ~30 pc and near-solar metallicities in the circumgalactic samples, while high-ionization metal absorption consistent with typical IGM densities and metallicities is visible in all samples.

Description: We present the results from a time domain study of absorption lines detected in quasar spectra with repeat observations from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7). Beginning with over 4500 unique time separation baselines of various absorption line species identified in the SDSS DR7 quasar spectra, we create a catalogue of 2522 quasar absorption line systems with two to eight repeat observations, representing the largest collection of unbiased and homogeneous multi-epoch absorption systems ever published. To investigate these systems for time variability of narrow absorption lines, we refine this sample based on the reliability of the system detection, the proximity of pixels with bright sky contamination to individual absorption lines and the quality of the continuum fit. Variability measurements of this sub-sample based on the absorption line equivalent widths yield a total of 33 systems with indications of significantly variable absorption strengths on time-scales ranging from one day to several years in the rest frame of the absorption system. Of these, at least 10 are from a class known as intervening absorption systems caused by foreground galaxies along the line of sight to the background quasar. This is the first evidence of possible absorption line variability detected in intervening systems, and their short time-scale variations suggest that small-scale structures (~10–100 au) are likely to exist in their host foreground galaxies.