A DEEP SEARCH FOR FAINT GALAXIES ASSOCIATED WITH VERY LOW REDSHIFT C iv ABSORBERS. III. THE MASS- AND ENVIRONMENT-DEPENDENT CIRCUMGALACTIC MEDIUM

• Main Authors: Burchett, Joseph N. (Author), Tripp, Todd M. (Author), Bordoloi, Rongmon (Contributor), Werk, Jessica K. (Author), Prochaska, J. Xavier (Author), Tumlinson, Jason (Author), Willmer, C. N. A. (Author), O'Meara, John (Author), Katz, Neal (Author)
• Other Authors: MIT Kavli Institute for Astrophysics and Space Research (Contributor)
• Format: Article
• Language: English
• Published: IOP Publishing, 2017-04-14T16:30:32Z.
• Subjects: Article
• Online Access: Get fulltext

 Using Hubble Space Telescope Cosmic Origins Spectrograph observations of 89 QSO sightlines through the Sloan Digital Sky Survey footprint, we study the relationships between C iv absorption systems and the properties of nearby galaxies, as well as the large-scale environment. To maintain sensitivity to very faint galaxies, we restrict our sample to 0.0015 < z < 0.015, which defines a complete galaxy survey to L ≳ 0.01 L* or stellar mass M*≳ 10⁸M [subscript ⊙]. We report two principal findings. First, for galaxies with impact parameter ρ < 1r[subscript vir], C IV detection strongly depends on the luminosity/stellar mass of the nearby galaxy. C IV is preferentially associated with galaxies with M[subscript *] > 10 [superscript 9.5] M [subscript ⊙] lower-mass galaxies rarely exhibit significant C IV absorption (covering fraction f [subscript C = 9 [ subscript-6] [subscript +12] % for 11 galaxies with M[subscript *] < 10 [superscript 9.5]M [subscript ⊙]. Second, C IV detection within the M* > 10 [superscript 9.5]M [subscript ⊙] population depends on environment. Using a fixed-aperture environmental density metric for galaxies with ρ < 160 kpc at z < 0.055, we find that 57 [ subscript -13] [superscript +12]% (8/14) of galaxies in low-density regions (regions with fewer than seven L > 0.15L* galaxies within 1.5 Mpc) have affiliated C IV absorption; however, none (0/7) of the galaxies in denser regions show C IV. Similarly, the C IV detection rate is lower for galaxies residing in groups with dark matter halo masses of M [subscript halo] > 10[superscript12.5]M [subscript ⊙]. In contrast to C IV, H i is pervasive in the circumgalactic medium without regard to mass or environment. These results indicate that C IV absorbers with logN(C IV) ≳13.5 [superscript -2 cm] trace the halos of M* > 10 [superscript 9.5]M[subscript ⊙] galaxies but also reflect larger-scale environmental conditions.