Misc,
A Deep Search For Faint Galaxies Associated With Very Low-redshift C IV Absorbers: III. A Galaxy Sample Complete to 0.01 L* and Evidence for Environmental Effects
(2015)cite arxiv:1512.00853Comment: 19 pages, 16 figures. Submitted to ApJ, comments welcome!.
Abstract
We employ a blindly selected sample of low-redshift C IV absorption systems
identified in spectra from the Hubble Space Telescope (HST) Cosmic Origins
Spectrograph (COS), combined with galaxy data from the Sloan Digital Sky Survey
(SDSS), to study the metal-enriched circumgalactic medium (CGM) with ~100%
completeness for galaxy luminosities L > 0.01 L* at z < 0.015. We find that
galaxies are typically found at the C IV absorber redshifts within impact
parameters rho < 200 kpc, with the nearest galaxy having L < 0.1 L* for 78% of
the absorbers. The ubiquity of faint dwarfs in close proximity to the absorbers
suggests that these galaxies affect the enrichment and physical conditions of
massive-galaxy halos. However, a fraction of our sample (33%) arise well
outside the virial radius of any nearby galaxy brighter than 0.01 L*. The
detection rate for C IV absorption within the virial radius is mass dependent
and is considerably higher for L >~0.1 L* galaxies (7/8) than for less luminous
galaxies (1/10). We also find that the occurrence of C IV absorbers depends
strongly on the broader environment: 67% (8/12) of galaxies with rho < 150 kpc
in regions of low galaxy density (regions with fewer than ten 0.1 L* galaxies
within 1 Mpc) have affiliated C IV absorption while none (0/9) of the galaxies
in denser regions show C IV within rho < 150 kpc. The reduced detection rate of
C IV in denser environments persists for massive group dark matter halos. In
contrast, H I is pervasive in the CGM without regard to mass or environment,
although some of these Ly-alpha absorbers could arise in unrelated
intergalactic gas.
