Kavli Affiliate: Donald G. York
| First 5 Authors: Varsha P. Kulkarni, David V. Bowen, Lorrie A. Straka, Donald G. York, Neeraj Gupta
| Summary:
We report {it HST} COS spectroscopy of 10 quasars with foreground
star-forming galaxies at 0.02$<$$z$$<$ 0.14 within impact parameters of
$sim$1-7 kpc. We detect damped/sub-damped Ly$alpha$ absorption in 100$%$ of
cases where no higher-redshift Lyman-limit systems extinguish the flux at the
expected wavelength of Ly$alpha$ 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 GBT 21-cm
emission measurements for 5 of the galaxies (including 2 detections). Combining
our sample with the literature, we construct a sample of 115 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
anti-correlated with impact parameter and stellar mass. More massive galaxies
appear to have gas-rich regions out to larger distances. The specific SFR
(sSFR) of absorbing galaxies increases with redshift and decreases with
$M^{ast}$, consistent with evolution of the star-formation main sequence
(SFMS). However, $sim$20$%$ of absorbing galaxies lie below the SFMS,
indicating that some DLA/sub-DLAs trace galaxies with longer-than-typical
gas-depletion time-scales. Most DLA/sub-DLA galaxies with 21-cm emission have
higher H I masses than typical galaxies with comparable $M^{ast}$. High
$M_{rm H I}/M^{ast}$ ratios and high sSFRs in DLA/sub-DLA galaxies with
$M^{ast}$$<$$10^{9}$$M_{odot}$ 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 galaxy-evolution studies to previously under-explored
regimes of low $M^{ast}$ and low SFR.
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