skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • Damped Lyα Absorbers in Star-forming Galaxies at z < 0.15 Detected with the Hubble Space Telescope and Implications for Galactic Evolution
Title: Damped Lyα Absorbers in Star-forming Galaxies at z < 0.15 Detected with the Hubble Space Telescope and Implications for Galactic Evolution
Abstract We report Hubble Space Telescope Cosmic Origins Spectrograph spectroscopy of 10 quasars with foreground star-forming galaxies at 0.02 < z < 0.14 within impact parameters of ∼1–7 kpc. We detect damped/sub-damped Ly α (DLA/sub-DLA) absorption in 100% of cases where no higher-redshift Lyman-limit systems extinguish the flux at the expected wavelength of Ly α absorption, obtaining the largest targeted sample of DLA/sub-DLAs in low-redshift galaxies. We present absorption measurements of neutral hydrogen and metals. Additionally, we present Green Bank Telescope 21 cm emission measurements for five of the galaxies (including two detections). Combining our sample with the literature, we construct a sample of 117 galaxies associated with DLA/sub-DLAs spanning 0 < z < 4.4, and examine trends between gas and stellar properties, and with redshift. The H i column density is anticorrelated with impact parameter and stellar mass. More massive galaxies appear to have gas-rich regions out to larger distances. The specific star formation rate (sSFR) of absorbing galaxies increases with redshift and decreases with M *, consistent with evolution of the star formation main sequence (SFMS). However, ∼20% of absorbing galaxies lie below the SFMS, indicating that some DLA/sub-DLAs trace galaxies with longer-than-typical gas-depletion timescales. Most DLA/sub-DLA galaxies with 21 cm emission have higher H i masses than typical galaxies with comparable M *. High M HI / M * ratios and high sSFRs in DLA/sub-DLA galaxies with M * < 10 9 M ⊙ suggest these galaxies may be gas-rich because of recent gas accretion rather than inefficient star formation. Our study demonstrates the power of absorption and emission studies of DLA/sub-DLA galaxies for extending galactic evolution studies to previously under-explored regimes of low M * and low SFR.  more » « less
Award ID(s):
2009811 2007538
PAR ID:
10351667
Author(s) / Creator(s):
; ; ; ; ; ;
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
More Like this
  1. ; ; ; ; (, The Astrophysical Journal)
    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 7 1 − 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. 
    more » « less
  2. ; ; ; ; ; ; ; ; ; ; et al (, Astronomy & Astrophysics)
    Context.One of the surprising early findings with JWST has been the discovery of a strong “roll-over” or a softening of the absorption edge of Lyαin a large number of galaxies atz≳ 6, in addition to systematic offsets from photometric redshift estimates and fundamental galaxy scaling relations. This has been interpreted as strong cumulative damped Lyαabsorption (DLA) wings from high column densities of neutral atomic hydrogen (H I), signifying major gas accretion events in the formation of these galaxies. Aims.To explore this new phenomenon systematically, we assembled the JWST/NIRSpec PRImordial gas Mass AssembLy (PRIMAL) legacy survey of 584 galaxies atz = 5.0 − 13.4, designed to study the physical properties and gas in and around galaxies during the reionization epoch. Methods.We characterized this benchmark sample in full and spectroscopically derived the galaxy redshifts, metallicities, star formation rates, and ultraviolet (UV) slopes. We defined a new diagnostic, the Lyαdamping parameterDLyα, to measure and quantify the net effect of Lyαemission strength, the H Ifraction in the intergalactic medium, or the local H Icolumn density for each source. The JWST-PRIMAL survey is based on the spectroscopic DAWN JWST Archive (DJA-Spec). We describe DJA-Spec in this paper, detailing the reduction methods, the post-processing steps, and basic analysis tools. All the software, reduced spectra, and spectroscopically derived quantities and catalogs are made publicly available in dedicated repositories. Results.We find that the fraction of galaxies showing strong integrated DLAs withNHI > 1021 cm−2only increases slightly from ≈60% atz ≈ 6 up to ≈65 − 90% atz > 8. Similarly, the prevalence and prominence of Lyαemission is found to increase with decreasing redshift, in qualitative agreement with previous observational results. Strong Lyαemitters (LAEs) are predominantly found to be associated with low-metallicity and UV faint galaxies. By contrast, strong DLAs are observed in galaxies with a variety of intrinsic physical properties, but predominantly at high redshifts and low metallicities. Conclusions.Our results indicate that strong DLAs likely reflect a particular early assembly phase of reionization-era galaxies, at which point they are largely dominated by pristine H Igas accretion. Atz = 8 − 10, this gas gradually cools and forms into stars that ionize their local surroundings, forming large ionized bubbles and producing strong observed Lyαemission atz < 8. 
    more » « less
  3. ; ; ; ; ; ; ; ; ; ; et al (, The Astrophysical Journal Letters)
    Abstract We present the discovery of neutral gas detected in both damped Lyαabsorption (DLA) and Hi21 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 Hibridge connecting two interacting dwarf galaxies (log (Mstar/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 (zQSO= 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 Hi21 cm emission is spatially coincident with the DLA at the 2σ–3σlevel per spectral channel over several adjacent beams. However, Hi21 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 ratioTs/fc> 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 Hi21 cm analyses will be critical for connecting the cosmic neutral gas content to galaxy environments. 
    more » « less
  4. ; ; ; ; ; ; (, The Astrophysical Journal)
    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 ≈ 56 − 24 + 38 % and ≈ 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× (αCO/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. 
    more » « less
  5. ; ; ; ; ; ; ; ; ; ; et al (, Monthly Notices of the Royal Astronomical Society)
    ABSTRACT Recent searches for the hosts of z ∼ 4 damped Ly α absorbers (DLAs) have detected bright galaxies at distances of tens of kpc from the DLA. Using the FIRE-2 cosmological zoom simulations, we argue that these relatively large distances are due to a predominantly cool and neutral inner circumgalactic medium (CGM) surrounding high-redshift galaxies. The inner CGM is cool because of the short cooling time of hot gas in $${\lesssim}10^{12}\, {\rm M_{\odot }}$$ haloes, which implies that accretion and feedback energy are radiated quickly, while it is neutral due to high volume densities and column densities at high redshift that shield cool gas from photoionization. Our analysis predicts large DLA covering factors ($${\gtrsim}50{{\ \rm per\ cent}}$$) out to impact parameters ∼0.3[(1 + z)/5]3/2Rvir from the central galaxies at z ≳ 1, equivalent to a proper distance of $${\sim}21\, M_{12}^{1/3} \left(\left(1+z\right)/5\right)^{1/2}\, {\rm kpc}$$ (Rvir and M12 are the halo virial radius and mass in units of $$10^{12}\, {\rm M_{\odot }}$$, respectively). This implies that DLA covering factors at z ∼ 4 may be comparable to unity out to a distance ∼10 times larger than stellar half-mass radii. A predominantly neutral inner CGM in the early universe suggests that its mass and metallicity can be directly constrained by absorption surveys, without resorting to the large ionization corrections as required for ionized CGM. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email