ALBERT

Description: We report a definitive detection of chemically enriched cool gas around massive quiescent galaxies at z 0.4–0.7. The result is based on a survey of 37 621 luminous red galaxy (LRG)-quasi-stellar object pairs in SDSS DR12 with projected distance d  〈 500 kpc. The LRGs are characterized by a predominantly old stellar population (age 1 Gyr) with 13 per cent displaying [O ii ] emission features and LINER-like spectra. Both passive and [O ii ]-emitting LRGs share the same stellar mass distribution with a mean of 〈log ( M * /M )〉 11.4 and a dispersion of 0.2 dex. Both LRG populations exhibit associated strong Mg ii absorbers out to d  〈 500 kpc. The mean gas covering fraction at d 120 kpc is $\langle \kappa \rangle _{\rm Mg\,\small {II}} 〉 15$  per cent and declines quickly to $\langle \kappa \rangle _{\rm Mg\,\small {II}} \approx 5$  per cent at d 500 kpc. No clear dependence on stellar mass is detected for the observed Mg ii absorption properties. The observed velocity dispersion of Mg ii -absorbing gas relative to either passive or [O ii ]-emitting LRGs is merely 60 per cent of what is expected from virial motion in these massive haloes. While no apparent azimuthal dependence is seen for $\langle \kappa \rangle _{\rm Mg\,\small {II}}$ around passive LRGs at all radii, a modest enhancement in $\langle \kappa \rangle _{\rm Mg\,\small {II}}$ is detected along the major axis of [O ii ]-emitting LRGs at d  〈 50 kpc. The suppressed velocity dispersion of Mg ii -absorbing gas around both passive and [O ii ]-emitting LRGs, together with an elevated $\langle \kappa \rangle _{\rm Mg\,\small {II}}$ along the major axis of [O ii ]-emitting LRGs at d  〈 50 kpc, provides important insights into the origin of the observed chemically enriched cool gas in LRG haloes. We consider different scenarios and conclude that the observed Mg ii absorbers around LRGs are best explained by a combination of cool clouds formed in thermally unstable LRG haloes and satellite accretion through filaments.

Description: We present a study of extended galaxy halo gas through H i and O vi absorption over two decades in projected distance at z   0.2. The study is based on a sample of 95 galaxies from a highly complete (〉80 per cent) survey of faint galaxies ( L  〉 0.1 L * ) with archival quasar absorption spectra and 53 galaxies from the literature. A clear anticorrelation is found between H i (O vi ) column density and virial radius normalized projected distance, d / R h . Strong H i (O vi ) absorption systems with column densities greater than 10 14.0 (10 13.5 ) cm –2 are found for 48 of 54 (36 of 42) galaxies at d 〈 R h indicating a mean covering fraction of $\langle \kappa _{\rm H\,\small {i}}\rangle =0.89$ ( $\langle \kappa _{\rm O\,\small {vi}}\rangle =0.86$ ). O vi absorbers are found at d    R h , beyond the extent observed for lower ionization species. At d / R h  = 1–3 strong H i (O vi ) absorption systems are found for only 7 of 43 (5 of 34) galaxies ( $\langle \kappa _{\rm H\,\small {i}}\rangle =0.16$ and $\langle \kappa _{\rm O\,\small {vi}}\rangle =0.15$ ). Beyond d  = 3 R h , the H i and O vi covering fractions decrease to levels consistent with coincidental systems. The high completeness of the galaxy survey enables an investigation of environmental dependence of extended gas properties. Galaxies with nearby neighbours exhibit a modest increase in O vi covering fraction at d  〉  R h compared to isolated galaxies ( $\kappa _{\rm O\,\small {vi}}\approx 0.13$ versus 0.04) but no excess H i absorption. These findings suggest that environmental effects play a role in distributing heavy elements beyond the enriched gaseous haloes of individual galaxies. Finally, we find that differential H i and O vi absorption between early- and late-type galaxies continues from d  〈  R h to d   3 R h .

Description: We present multisightline absorption spectroscopy of cool gas around three lensing galaxies at z  = 0.4–0.7. These lenses have half-light radii r e  = 2.6–8 kpc and stellar masses of log M * /M = 10.9–11.4, and therefore resemble nearby passive elliptical galaxies. The lensed QSO sightlines presented here occur at projected distances of d  = 3–15 kpc (or d 1–2 r e ) from the lensing galaxies, providing for the first time an opportunity to probe both interstellar gas at r  ~  r e and circumgalactic gas at larger radii r  〉〉  r e of these distant quiescent galaxies. We observe distinct gas absorption properties among different lenses and among sightlines of individual lenses. Specifically, while the quadruple lens for HE 0435–1223 shows no absorption features to very sensitive limits along all four sightlines, strong Mg ii , Fe  ii , Mg  i , and Ca  ii absorption transitions are detected along both sightlines near the double lens for HE 0047–1756, and in one of the two sightlines near the double lens for HE 1104–1805. The absorbers are resolved into 8–15 individual components with a line-of-sight velocity spread of v 300–600 km s –1 . The large ionic column densities, log N 14, observed in two components suggest that these may be Lyman limit or damped Ly α absorbers with a significant neutral hydrogen fraction. The majority of the absorbing components exhibit a uniform supersolar Fe/Mg ratio with a scatter of 〈0.1 dex across the full v range. Given a predominantly old stellar population in these lensing galaxies, we argue that the observed large velocity width and Fe-rich abundance pattern can be explained by SNe Ia enriched gas at radius r  ~  r e . We show that additional spatial constraints in line-of-sight velocity and relative abundance ratios afforded by a multisightline approach provide a powerful tool to resolve the origin of chemically enriched cool gas in massive haloes.

Description: Previous observations of quasar host haloes at z   2 have uncovered large quantities of cool gas that exceed what is found around inactive galaxies of both lower and higher masses. To better understand the source of this excess cool gas, we compiled an exhaustive sample of 195 quasars at z   1 with constraints on chemically enriched, cool gas traced by Mg ii absorption in background quasar spectra from the Sloan Digital Sky Survey. This quasar sample spans a broad range of luminosities from L bol  = 10 44.4 to 10 46.8 erg s –1 and allows an investigation of whether halo gas properties are connected with quasar properties. We find a strong correlation between luminosity and cool gas covering fraction. In particular, low-luminosity quasars exhibit a mean gas covering fraction comparable to inactive galaxies of similar masses, but more luminous quasars exhibit excess cool gas approaching what is reported previously at z   2. Moreover, 30–40 per cent of the Mg ii absorption occurs at radial velocities of | v | 〉 300 km s –1  from the quasar, inconsistent with gas bound to a typical quasar host halo. The large velocity offsets and observed luminosity dependence of the cool gas near quasars can be explained if the gas arises from: (1) neighbouring haloes correlated through large-scale structure at Mpc scales, (2) feedback from luminous quasars or (3) debris from the mergers thought to trigger luminous quasars. The first of these scenarios is in tension with the lack of correlation between quasar luminosity and clustering while the latter two make distinct predictions that can be tested with additional observations.