DIISC-VI (COS-DIISC): Ultraviolet Metal Absorption Relative to the H i Disk of Galaxies

Abstract

As part of the Deciphering the Interplay between the Interstellar medium, Stars, and the Circumgalactic medium (DIISC) survey, we present the UV metal absorption features in the circumgalactic medium (CGM) near the H i gas disk (<4.5RHI) of 31 nearby galaxies through quasar absorption-line spectroscopy. Of the ions under study, Si iiiλ1206 was most frequently detected (18 of 31 sight lines), while C iiλ1334 and Si iiλ1260 were detected in 17 and 15 of 31 sight lines, respectively. Many components were consistent with photoionization equilibrium models; most of the cold and cool gas phase clouds were found to have lengths smaller than 2 kpc. Sight lines with smaller impact parameters (ρ) normalized by the galaxy’s virial radius (Rvir) and H i radius (RHI) tend to have more components and larger rest-frame equivalent widths (Wr) than those that probe the CGM at larger radii. In particular, we find that the location of metals are better traced by ρ/RHI rather than the traditional ρ/Rvir. Larger covering fractions are found closer to galaxies, with a radial decline that depends on the Wr limit used. Our results provide new insights into the spatial distribution of metals around the H i disks of low-redshift galaxies.