The COS-legacy survey of C IV absorbers: properties and origins of the intervening systems

Abstract

We present here results from a survey of intervening C IV absorbers at $z<0.16$ conducted using 223 sightlines from the Hubble Spectroscopic Legacy Archive. Most systems (83%) out of the total sample of 69 have simple kinematics with 1 or 2 C IV components. In the 22 C IV systems with well constrained H I column densities, the temperatures from the $b$-values imply predominantly photoionized plasma ($T\le 10^5$ K) and non-thermal dynamics. These systems also have solar or higher metallicities. We obtain a C IV line density of $d\mathcal{N}/dX=5.1\pm 1.0$ for $\log [N(CIV)(c{m}^{-2})]\ge 12.9$, and ${\Omega }_{CIV}=(8.01\pm 1.62)\times 10^{-8}$ for $12.9\le \log [N(CIV)(c{m}^{-2})]\le 15.0$. The C IV bearing diffuse gas in the $z<0.16$ Universe has a metallicity of $(2.07\pm 0.43)\times 10^{-3}$ Z${}_{\odot }$, an order of magnitude more than the metal abundances in the IGM at high redshifts ($z\gtrsim 5$), and consistent with the slow build-up of metals in the diffuse circum/intergalactic space with cosmic time. For $z<0.015$ (complete above $L>0.01L^{\star }$), the Sloan Digital Sky Survey provides a tentative evidence of declining covering fraction for strong C IV ($N>10^{13.5}c{m}^{-2}$) with $\rho$ (impact parameter) and $\rho /R_{\mathrm{vir}}$. However, the increase at high separations suggests that strong systems are not necessarily coincident with such galaxies. We also find that strong C IV absorption at $z<0.051$ is not coincident with galaxy over-dense regions complete for $L>0.13L^{\star }$

Published in MNRAS. Modified to match the text in the published version. 20 pages, 16 figures, 4 tables. The system plots, measurement tables, and discussions on origins of some individual systems, are available online at MNRAS. The link to the supplementary information is present in this arxiv version

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• Metal-enriched halo gas across galaxy overdensities over the last 10 billion years
• Examining the Decline in the C IV Content of the Universe over 4.3 < z < 6.3 using the E-XQR-30 Sample
• Probing the physicochemical properties of the Leo Ring and the Leo I group
• The environments and hosts of metal absorption at z>5