# The Last Eight-Billion Years of Intergalactic CIV Evolution - Astrophysics > Cosmology and Nongalactic Astrophysics

The Last Eight-Billion Years of Intergalactic CIV Evolution - Astrophysics > Cosmology and Nongalactic Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: We surveyed the HST UV spectra of 49 low-redshift quasars for z < 1 CIVcandidates, relying solely on the characteristic wavelength separation of thedoublet. After consideration of the defining traits of CIV doublets e.g.,consistent line profiles, other associated transitions, etc., we defined asample of 38 definite group G = 1 and five likely G = 2 doublets with restequivalent widths W r for both lines detected at >= 3 sigma. We conductedMonte-Carlo completeness tests to measure the unblocked redshift dz andco-moving pathlength dX over which we were sensitive to CIV doublets of arange of equivalent widths and column densities. The absorber line density ofG = 1+2 doublets is dN-dX = 4.1+0.7-0.6 for log NC^+3 >= 13.2, and dN-dXhas not evolved significantly since z = 5. The best-fit power-law to the G = 1frequency distribution of column densities fNC^+3 = kNC^+3-N 0^alpha Nhas coefficient k = 0.67+0.18-0.16 x 10^-14 cm^2 and exponent alpha N =-1.50+0.17-0.19, where N 0 = 10^14 cm^-2. Using the power-law model offNC^+3, we measured the C^+3 mass density relative to the critical density:OmegaC^+3 = 6.20+1.82-1.52 x 10^-8 for 13 <= log NC^+3 <= 15. This valueis a 2.8+-0.7 increase in OmegaC^+3 compared to the error-weighted mean fromseveral 1 < z < 5 surveys for CIV absorbers. A simple linear regression toOmegaC^+3 over the age of the Universe indicates that OmegaC^+3 has slowlybut steadily increased from z = 5 -> 0, with dOmegaC^+3-dt age =0.42+-0.2 x 10^-8 Gyr^-1.

Author: ** Kathy L. Cooksey 1, Christopher Thom 2, J. Xavier Prochaska 1,3, Hsiao-Wen Chen 2 1 UC Santa Cruz; 2 U Chicago; 3 UCO-Lick Observ**

Source: https://arxiv.org/