Damped Ly-alpha Absorbers in Star-forming Galaxies at z < 0.15 Detected
  with the Hubble Space Telescope and Implications for Galaxy Evolution
  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.
