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: We report the discovery of 13 confirmed two-image quasar lenses from a systematic search for gravitationally lensed quasars in the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). We adopted a methodology similar to that used in the SDSS Quasar Lens Search (SQLS). In addition to the confirmed lenses, we report 11 quasar pairs with small angular separations ( 2 arcsec) confirmed from our spectroscopy, which are either projected pairs, physical binaries, or possibly quasar lens systems whose lens galaxies have not yet been detected. The newly discovered quasar lens system, SDSS J1452+4224 at z s 4.8 is one of the highest redshift multiply imaged quasars found to date. Furthermore, we have over 50 good lens candidates yet to be followed up. Owing to the heterogeneous selection of BOSS quasars, the lens sample presented here does not have a well-defined selection function.

Description: Using the Low Dispersion Survey Spectrograph 3 at the Magellan II Clay Telescope, we target candidate absorption host galaxies detected in deep optical imaging (reaching limiting apparent magnitudes of 23.0–26.5 in g , r , i , and z filters) in the fields of three QSOs, each of which shows the presence of high metallicity, high $N_{\rm H\,\small {i}}$ absorption systems in their spectra (Q0826-2230: z abs = 0.9110, Q1323-0021: z abs = 0.7160, Q1436-0051: z abs = 0.7377, 0.9281). We confirm three host galaxies at redshifts 0.7387, 0.7401, and 0.9286 for two of the Lyman α absorption systems (one with two galaxies interacting). For these systems, we are able to determine the star formation rates (SFRs); impact parameters (from previous imaging detections); the velocity shift between the absorption and emission redshifts; and, for one system, also the emission metallicity. Based on previous photometry, we find these galaxies have L 〉 L *. The [O ii ] SFRs for these galaxies are in the range 11–25 M  yr –1 (uncorrected for dust), while the impact parameters lie in the range 35–54 kpc. Despite the fact that we have confirmed galaxies at 50 kpc from the QSO, no gradient in metallicity is indicated between the absorption metallicity along the QSO line of sight and the emission line metallicity in the galaxies. We confirm the anticorrelation between impact parameter and $N_{\rm H\,\small {i}}$ from the literature. We also report the emission redshift of five other galaxies: three at z em 〉 z QSO , and two ( L 〈 L *) at z em 〈 z QSO not corresponding to any known absorption systems.

Description: We exploit stellar population models of absorption line indices in the ultraviolet (from 2000 to 3200 Å) to study the spectra of massive galaxies. Our central aim is to investigate the occurrence at high redshift of the UV upturn, i.e. the increased UV emission due to old stars observed in massive galaxies and spiral bulges in the local Universe. We use a large (~275 000) sample of z  ~ 0.6 massive ( M */M  〉 11.5) galaxies using both individual spectra and stacks and employ a suite of models including a UV contribution from old populations, spanning various effective temperatures, fuel consumptions and metallicities. We find that a subset of our indices; Mg i , Fe i , and BL3096, are able to differentiate between old and young UV ages. We find evidence for old stars contributing to the UV in massive galaxies, rather than star formation. The data favour models with low/medium upturn temperatures (10 000–25 000 K) consistent with local galaxies, depending on the assumed metallicity, and with a larger fuel ( $f \sim 6.5\times 10^{-2}\, \rm {M}_{{\odot }}$ ). Models with one typical temperature are favoured over models with a temperature range, which would be typical of an extended horizontal branch. Old UV-bright populations are found in the whole galaxy sample (92 per cent), with a mass fraction peaking around 20–30 per cent. Upturn galaxies are massive and have redder colours, in agreement with findings in the local Universe. We find that the upturn phenomenon appears at z  ~ 1 and its frequency increases towards lower redshift, as expected by stellar evolution of low-mass stars. Our findings will help constrain stellar evolution in the exotic UV upturn phase.

Description: We present photometric and spectroscopic measurements of 53 QSO–galaxy pairs from the Sloan Digital Sky Survey (SDSS), where nebular emission lines from a 0 〈 z 〈 0.84 foreground galaxy are detected in the fibre spectra of a background QSO, bringing the overall sample to 103 QSO–galaxy pairs detected in the SDSS. We here study the nature of these systems. Detected foreground galaxies appear at impact parameters between 0.37 and 12.68 kpc. The presence of oxygen and Balmer emission lines allows us to determine the emission line metallicities for our sample, which are on average supersolar in value. Star formation rates for our sample are in the range 0.01–12 M  yr –1 . We utilize photometric redshift fitting techniques to estimate the M * values of our galaxies (log M * = 7.34–11.54), and extrapolate this relationship to those galaxies with no imaging detections. Where available, we measure the absorption features present in the QSO spectrum due to the foreground galaxy and the relationships between their rest equivalent widths. We report an anticorrelation between impact parameter and E ( B  –  V ) ( g  –  i ) , as well as a correlation between galaxy colour ( u  –  r ) and E ( B  –  V ) ( g  –  i ) . We find that our sample is one of late-type, star-forming galaxies comparable to field galaxies in a similar redshift range, providing important clues to better understand absorption systems. These galaxies represent a sample of typical galaxies in the local Universe for which abundances, extinction, morphology, and absorption properties may be measured using background QSOs with great potential for follow-up observations.

Description: We present a tentative detection of the large-scale structure of Ly α emission in the Universe at redshifts z = 2–3.5 by measuring the cross-correlation of Ly α surface brightness with quasars in Sloan Digital Sky Survey/Baryon Oscillation Spectroscopic Survey. We use a million spectra targeting luminous red galaxies at z 〈 0.8, after subtracting a best-fitting model galaxy spectrum from each one, as an estimate of the high-redshift Ly α surface brightness. The quasar–Ly α emission cross-correlation is detected on scales 1 ~ 15 h –1 Mpc, with shape consistent with a CDM model with $\Omega _{\rm m} =0.30^{+0.10}_{-0.07}$ . The predicted amplitude of this cross-correlation is proportional to the product of the mean Ly α surface brightness, 〈μ α 〉, the amplitude of mass fluctuations and the quasar and Ly α emission bias factors. We infer 〈μ α 〉 ( b α /3) = (3.9 ± 0.9) x 10 –21 erg s –1  cm –2 Å –1  arcsec –2 , where b α is the Ly α emission bias. If star-forming galaxies dominate this emission, we find SFR = (0.28 ± 0.07)(3/ b α ) yr –1  Mpc –3 . For b α = 3, this value is ~30 times larger than previous estimates from individually detected Ly α emitters, but consistent with the total SFR derived from dust-corrected, continuum UV galaxy surveys, if most of the Ly α photons from these galaxies avoid dust absorption and are reemitted after diffusing in large gas haloes. Heating of intergalactic gas by He ii photoionization from quasar radiation or jets may alternatively explain the detected correlation, and cooling radiation from gas in galactic haloes may also contribute. We also detect redshift space anisotropy of the quasar–Ly α emission cross-correlation, finding evidence at the 3.0 level that it is radially elongated, which may be explained by radiative-transfer effects. Our measurements represent the first application of the intensity mapping technique to optical observations.

Description: The use of background quasars provides a powerful tool to probe the cool gas in the circumgalactic medium of foreground galaxies. Here, we present new observations with SINFONI and X-Shooter of absorbing-galaxy candidates at z = 0.7–1. We report the detection with both instruments of the Hα emission line of one sub-damped Lyman α (sub-DLA) at z abs = 0.941 87 with $\log N({\rm H}\,{\small {I}})$ = 19.38 $^{+0.10}_{-0.15}$ towards SDSS J002133.27+004300.9. We estimate the star formation rate: SFR = 3.6 ± 2.2 M  yr –1 in that system. A detailed kinematic study indicates a dynamical mass M dyn = 10 9.9±0.4 M and a halo mass M halo = 10 11.9±0.5 M . In addition, we report the [O ii ] detection with X-Shooter of another DLA at z abs = 0.7402 with $\log N({\rm H}\,{\small {I}})$ = 20.4 ± 0.1 towards Q0052+0041 and an estimated SFR of 5.3 ± 0.7 M  yr –1 . Three other objects are detected in the continuum with X-Shooter but the nature and redshift of two of these objects are unconstrained due to the absence of emission lines, while the third object might be at the redshift of the quasar. We use the objects detected in our whole $N({\rm H}\,{\small {I}})$ -selected SINFONI survey to compute the metallicity difference between the galaxy and the absorbing gas, $\delta _{\rm H\,\small {I}}(X)$ , where a positive (negative) value indicates infall (outflow). We compare this quantity with the quasar line-of-sight alignment with the galaxy's major (minor) axis, another tracer of infall (outflow). We find that these quantities do not correlate as expected from simple assumptions. Additional observations are necessary to relate these two independent probes of gas flows around galaxies.