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Abstract We present a survey undertaken with the Atacama Large Millimeter/submillimeter Array (ALMA) to study the galaxies associated with a representative sample of 16 damped Lyαabsorbers (DLAs) atz ≈ 4.1–4.5, using the [Cii] 158μm ([Cii]) line. We detect seven [Cii]-emitting galaxies in the fields of five DLAs, all of which have absorption metallicity [M/H] > −1.5. We find that the detectability of these Hi-selected galaxies with ALMA is a strong function of DLA metallicity, with a detection rate of $71_{-20}^{+11}$% for DLAs with [M/H] > −1.5 and 0⁺¹⁸% for DLAs with [M/H] < −1.5. The identified DLA galaxies have far-IR properties similar to those of typical star-forming galaxies atz ∼ 4, with estimated obscured star formation rates ranging from ≲6M_⊙yr⁻¹to 110M_⊙yr⁻¹. High-metallicity DLAs therefore provide an efficient way to identify and study samples of high-redshift, star-forming galaxies, without preselecting the galaxies by their emission properties. The agreement between the velocities of the metal absorption lines of the DLA and the [Cii] emission line of the DLA galaxy indicates that the metals within the DLA originated in the galaxy. With observed impact parameters between 14 and 59 kpc, this indicates that star-forming galaxies atz ∼ 4 have a substantial reservoir of dense, cold, neutral gas within their circumgalactic medium that has been enriched with metals from the galaxy. 

Abstract We use the Karl G. Jansky Very Large Array (VLA) and the Atacama Large Millimeter/submillimeter Array to detect CO(1–0), CO(3–2), and rest-frame 349 GHz continuum emission from an Hi-selected galaxy, DLA1020+2733g, atz ≈ 2.3568 in the field of thez= 2.3553 damped Lyαabsorber (DLA) toward QSO J1020+2733. The VLA CO(1–0) detection yields a molecular gas mass of (2.84 ± 0.42) × 10¹¹ × (α_CO/4.36)M_⊙, the largest ever measured in an Hi-selected galaxy. The DLA metallicity is +0.28 ± 0.16, from the Zniiλ2026 absorption line detected in a Keck Echellette Spectrograph and Imager spectrum. This continues the trend of high-metallicity DLAs being frequently associated with massive galaxies. We obtain a star formation rate (SFR) of ≲400M_⊙yr⁻¹from the rest-frame 349 GHz continuum emission and a relatively long molecular gas depletion timescale of ≳0.6 Gyr. The excitation of theJ= 3 rotational level is subthermal, with $r_{31}\equiv L{\prime }_{\mathrm{CO}(3-2)}/L{\prime }_{\mathrm{CO}(1-0)}=0.513\pm 0.081$, suggesting that DLA1020+2733g has a low SFR surface density. The large velocity spread of the CO lines, ≈500 km s⁻¹, and the long molecular gas depletion timescale suggest that DLA1020+2733g is likely to be a cold rotating-disk galaxy. 

Abstract We report that the neutral hydrogen (Hi) mass density of the Universe (ρ_Hi) increases with cosmic time sincez ∼ 5, peaks atz ∼ 3, and then decreases towardz ∼ 0. This is the first result of Qz5, our spectroscopic survey of 63 quasars atz ≳ 5 with VLT/X-SHOOTER and Keck/ESI aimed at characterizing intervening Higas absorbers atz ∼ 5. The main feature of Qz5 is the high resolution (R ∼ 7000–9000) of the spectra, which allows us to (1) accurately detect high column density Higas absorbers in an increasingly neutral intergalactic medium atz ∼ 5 and (2) determine the reliability of previousρ_Himeasurements derived with lower resolution spectroscopy. We find five intervening damped Lyαabsorbers (DLAs) atz > 4.5, which corresponds to the lowest DLA incidence rate ( $0.034_{0.02}^{0.05}$) atz ≳ 2. We also measure the lowestρ_Hiatz ≳ 2 from our sample of DLAs and subDLAs, corresponding toρ_Hi $=0.56_{0.31}^{0.82}\times 10^8{M}_{\odot }$Mpc⁻³atz ∼ 5. Taking into account our measurements atz ∼ 5 and systematic biases in the DLA detection rate at lower spectral resolutions, we conclude thatρ_Hidoubles fromz ∼ 5 toz ∼ 3. From these results emerges a qualitative agreement between how the cosmic densities of Higas mass, molecular gas mass, and star formation rate build up with cosmic time. 

Abstract We present Keck Cosmic Web Imager Lyαintegral field spectroscopy of the fields surrounding 14 damped Lyαabsorbers (DLAs) atz≈ 2. Of these 14 DLAs, nine have high metallicities ([M/H] > − 0.3), and four of those nine feature a CO-emitting galaxy at an impact parameter ≲30 kpc. Our search reaches median Lyαline flux sensitivities of ∼2 × 10⁻¹⁷erg s⁻¹cm⁻²over apertures of ∼6 kpc and out to impact parameters of ∼50 kpc. We recover the Lyαflux of three known Lyα-emitting Hi-selected galaxies in our sample. In addition, we find two Lyαemitters at impact parameters of ≈50–70 kpc from the high-metallicity DLA atz≈ 1.96 toward QSO B0551-366. This field also contains a massive CO-emitting galaxy at an impact parameter of ≈15 kpc. Apart from the field with QSO B0551-366, we do not detect significant Lyαemission in any of the remaining eight high-metallicity DLA fields. Considering the depth of our observations and our ability to recover previously known Lyαemitters, we conclude that Hi-selected galaxies associated with high-metallicity DLAs atz≈ 2 are dusty and therefore might feature low Lyαescape fractions. Our results indicate that complementary approaches—using Lyα, CO, Hα, and [Cii] 158μm emission—are necessary to identify the wide range of galaxy types associated withz≈ 2 DLAs. 

Abstract We report a Karl G. Jansky Very Large Array search for redshifted CO(1–0) emission from three Hi-absorption-selected galaxies atz≈ 2, identified earlier in their CO(3–2) or CO(4–3) emission. We detect CO(1–0) emission from DLA B1228-113 atz≈ 2.1933 and DLA J0918+1636 atz≈ 2.5848; these are the first detections of CO(1–0) emission in high-zHi-selected galaxies. We obtain high molecular gas masses,M_mol≈ 10¹¹× (α_CO/4.36)M_⊙, for the two objects with CO(1–0) detections, which are a factor of ≈1.5–2 lower than earlier estimates. We determine the excitation of the mid-JCO rotational levels relative to theJ= 1 level,r_J1, in Hi-selected galaxies for the first time, obtainingr₃₁= 1.00 ± 0.20 andr₄₁= 1.03 ± 0.23 for DLA J0918+1636, andr₃₁= 0.86 ± 0.21 for DLA B1228-113. These values are consistent with thermal excitation of theJ= 3 andJ= 4 levels. The excitation of theJ= 3 level in the Hi-selected galaxies is similar to that seen in massive main-sequence and submillimeter galaxies atz≳2, but higher than that in main-sequence galaxies atz≈ 1.5; the higher excitation of the galaxies atz≳ 2 is likely to be due to their higher star formation rate (SFR) surface density. We use Hubble Space Telescope Wide Field Camera 3 imaging to detect the rest-frame near-ultraviolet (NUV) emission of DLA B1228-113, obtaining an NUV SFR of 4.44 ± 0.47M_⊙yr⁻¹, significantly lower than that obtained from the total infrared luminosity, indicating significant dust extinction in thez≈ 2.1933 galaxy. 

Abstract We report a NOrthern Extended Millimeter Array (NOEMA) and Atacama Large Millimeter/submillimeter Array search for redshifted CO emission from the galaxies associated with seven high-metallicity ([M/H] ≥ −1.03) damped Lyαabsorbers (DLAs) atz≈ 1.64–2.51. Our observations yielded one new detection of CO(3–2) emission from a galaxy atz= 2.4604 using NOEMA, associated with thez= 2.4628 DLA toward QSO B0201+365. Including previous searches, our search results in detection rates of CO emission of $\approx {56}_{-24}^{+38}$% and $\approx {11}_{-9}^{+26}$%, respectively, in the fields of DLAs with [M/H] > −0.3 and [M/H] < −0.3. Further, the Hi–selected galaxies associated with five DLAs with [M/H] > −0.3 all have high molecular gas masses, ≳5 × 10¹⁰M_⊙. This indicates that the highest-metallicity DLAs atz≈ 2 are associated with the most massive galaxies. The newly identifiedz≈ 2.4604 Hi–selected galaxy, DLA0201+365g, has an impact parameter of ≈7 kpc to the QSO sightline, and an implied molecular gas mass of (5.04 ± 0.78) × 10¹⁰× (α_CO/4.36) × (r₃₁/0.55)M_⊙. Archival Hubble Space Telescope Wide Field and Planetary Camera 2 imaging covering the rest-frame near-ultraviolet (NUV) and far-ultraviolet (FUV) emission from this galaxy yield nondetections of rest-frame NUV and FUV emission, and a 5σupper limit of 2.3M_⊙yr⁻¹on the unobscured star formation rate (SFR). The low NUV-based SFR estimate, despite the very high molecular gas mass, indicates that DLA0201+365g either is a very dusty galaxy, or has a molecular gas depletion time that is around 2 orders of magnitude larger than that of star-forming galaxies at similar redshifts.