The last eight-billion years of intergalactic CIV evolution

Abstract

We surveyed the Hubble Space Telescope UV spectra of 49 low-redshift quasars for z < 1 C IV candidates, relying solely on the characteristic wavelength separation of the doublet. After consideration of the defining traits of C IV doublets (e.g., consistent line profiles, other associated transitions, etc.), we defined a sample of 38 definite (group G = 1) and five likely (G = 2) doublets with rest equivalent widths Wr for both lines detected at . We conducted Monte Carlo completeness tests to measure the unblocked redshift (Δz) and co-moving path length (ΔX) over which we were sensitive to C IV doublets of a range of equivalent widths and column densities. The absorber line density of (G = 1+2) doublets is for log N(C+3) ≥ 13.2, and has not evolved significantly since z = 5. The best-fit power law to the G = 1 frequency distribution of column densities has coefficient k = 0.67 +0.18-0.16 × 10-14 cm2 and exponent αN = -1.50+0.17-0.19, where N 0 = 1014 cm-2. Using the power-law model of f(N(C+3)), we measured the C+3 mass density relative to the critical density: for 13 ≤ log N(C+3) ≤ 15. This value is a 2.8 0.7 increase in compared to the error-weighted mean from several 1 < z < 5 surveys for C IV absorbers. A simple linear regression to over the age of the universe indicates that has slowly but steadily increased from z = 5 → 0, with. © 2010. The American Astronomical Society.