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 Ly
- NSF-PAR ID:
- 10351667
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 929
- Issue:
- 2
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 150
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract α absorbers (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 % and %, 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) × (r 31/0.55)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 5σ upper 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. -
Abstract We present the discovery of neutral gas detected in both damped Ly
α absorption (DLA) and Hi 21 cm emission outside of the stellar body of a galaxy, the first such detection in the literature. A joint analysis between the Cosmic Ultraviolet Baryon Survey and the MeerKAT Absorption Line Survey reveals an Hi bridge connecting two interacting dwarf galaxies (log (M star/M ⊙) = 8.5 ± 0.2) that host az = 0.026 DLA with log[N (Hi )/cm−2] = 20.60 ± 0.05 toward the QSO J2339−5523 (z QSO= 1.35). At impact parameters ofd = 6 and 33 kpc, the dwarf galaxies have no companions more luminous than ≈0.05L *within at least Δv = ±300 km s−1andd ≈ 350 kpc. The Hi 21 cm emission is spatially coincident with the DLA at the 2σ –3σ level per spectral channel over several adjacent beams. However, Hi 21 cm absorption is not detected against the radio-bright QSO; if the background UV and radio sources are spatially aligned, the gas is either warm or clumpy (with a spin temperature to covering factor ratioT s /f c > 1880 K). Observations with VLT-MUSE demonstrate that theα -element abundance of the ionized interstellar medium (ISM) is consistent with the DLA (≈10% solar), suggesting that the neutral gas envelope is perturbed ISM gas. This study showcases the impact of dwarf–dwarf interactions on the physical and chemical state of neutral gas outside of star-forming regions. In the SKA era, joint UV and Hi 21 cm analyses will be critical for connecting the cosmic neutral gas content to galaxy environments. -
ABSTRACT We examine the properties of damped Lyman-α absorbers (DLAs) emerging from a single set of cosmological initial conditions in two state-of-the-art cosmological hydrodynamic simulations: simba and technicolor dawn. The former includes star formation and black hole feedback treatments that yield a good match with low-redshift galaxy properties, while the latter uses multifrequency radiative transfer to model an inhomogeneous ultraviolet background (UVB) self-consistently and is calibrated to match the Thomson scattering optical depth, UVB amplitude, and Ly α forest mean transmission at z > 5. Both simulations are in reasonable agreement with the measured stellar mass and star formation rate functions at z ≥ 3, and both reproduce the observed neutral hydrogen cosmological mass density, $\Omega _{\rm H\, \small{I}}(z)$. However, the DLA abundance and metallicity distribution are sensitive to the galactic outflows’ feedback and the UVB amplitude. Adopting a strong UVB and/or slow outflows underproduces the observed DLA abundance, but yields broad agreement with the observed DLA metallicity distribution. By contrast, faster outflows eject metals to larger distances, yielding more metal-rich DLAs whose observational selection may be more sensitive to dust bias. The DLA metallicity distribution in models adopting an H2-regulated star formation recipe includes a tail extending to [M/H] ≪ −3, lower than any DLA observed to date, owing to curtailed star formation in low-metallicity galaxies. Our results show that DLA observations play an important role in constraining key physical ingredients in galaxy formation models, complementing traditional ensemble statistics such as the stellar mass and star formation rate functions.
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Abstract We use medium- and high-resolution spectroscopy of close pairs of quasars to analyze the circumgalactic medium (CGM) surrounding 32 damped Ly
α absorption systems (DLAs). The primary quasar sightline in each pair probes an intervening DLA in the redshift range 1.6 <z abs< 3.5, such that the secondary sightline probes absorption from Lyα and a large suite of metal-line transitions (including Oi , Cii , Civ , Siii , and Siiv ) in the DLA host galaxy’s CGM at transverse distances 24 kpc ≤R ⊥≤ 284 kpc. Analysis of Lyα in the CGM sightlines shows an anticorrelation betweenR ⊥and Hi column density (N HI) with 99.8% confidence, similar to that observed around luminous galaxies. The incidences of Cii and Siii withN > 1013cm−2within 100 kpc of DLAs are larger by 2σ than those measured in the CGM of Lyman break galaxies (Cf (N CII ) > 0.89 and ). Metallicity constraints derived from ionic ratios for nine CGM systems with negligible ionization corrections andN HI> 1018.5cm−2show a significant degree of scatter (with metallicities/limits across the range ), suggesting inhomogeneity in the metal distribution in these environments. Velocity widths of Civ λ 1548 and low-ionization metal species in the DLA versus CGM sightlines are strongly (>2σ ) correlated, suggesting that they trace the potential well of the host halo overR ⊥≲ 300 kpc scales. At the same time, velocity centroids for Civ λ 1548 differ in DLA versus CGM sightlines by >100 km s−1for ∼50% of velocity components, but few components have velocities that would exceed the escape velocity assuming dark matter host halos of ≥1012M ⊙. -
Abstract The H i gas content is a key ingredient in galaxy evolution, the study of which has been limited to moderate cosmological distances for individual galaxies due to the weakness of the hyperfine H i 21 cm transition. Here we present a new approach that allows us to infer the H i gas mass M HI of individual galaxies up to z ≈ 6, based on a direct measurement of the [C ii ]-to-H i conversion factor in star-forming galaxies at z ≳ 2 using γ -ray burst afterglows. By compiling recent [C ii ]-158 μ m emission line measurements we quantify the evolution of the H i content in galaxies through cosmic time. We find that M HI starts to exceed the stellar mass M ⋆ at z ≳ 1, and increases as a function of redshift. The H i fraction of the total baryonic mass increases from around 20% at z = 0 to about 60% at z ∼ 6. We further uncover a universal relation between the H i gas fraction M HI / M ⋆ and the gas-phase metallicity, which seems to hold from z ≈ 6 to z = 0. The majority of galaxies at z > 2 are observed to have H i depletion times, t dep,HI = M HI /SFR, less than ≈2 Gyr, substantially shorter than for z ∼ 0 galaxies. Finally, we use the [C ii ]-to-H i conversion factor to determine the cosmic mass density of H i in galaxies, ρ HI , at three distinct epochs: z ≈ 0, z ≈ 2, and z ∼ 4–6. These measurements are consistent with previous estimates based on 21 cm H i observations in the local universe and with damped Ly α absorbers (DLAs) at z ≳ 2, suggesting an overall decrease by a factor of ≈5 in ρ HI ( z ) from the end of the reionization epoch to the present.more » « less