NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-06-18 T16:31:19 PDT
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For refcode 2010ApJ...708..868C:
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2010ApJ...708..868C The Last Eight-Billion Years of Intergalactic C IV Evolution Cooksey, Kathy L.; Thom, Christopher; Prochaska, J. Xavier; Chen, Hsiao-Wen 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 W_r_ for both lines detected at >= 3{sigma}_W_r_. We conducted Monte Carlo completeness tests to measure the unblocked redshift ({DELTA}z) and co-moving path length ({DELTA}X) 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 dN_CIV_/dX= 4.1^+0.7^_-0.6_ for log N(C^+3^) >= 13.2, and dN_CIV_/dX has not evolved significantly since z = 5. The best-fit power law to the G = 1 frequency distribution of column densities f(N(C^+3^)) {approx} k(N(C^+3^)/N_0_)^{alpha}^_N_ has 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 of f(N(C^+3^)), we measured the C^+3^ mass density relative to the critical density: {OMEGA}_C_^+3^= (6.20^+1.82^_-1.52_) x 10^-8^ for 13 <= log N(C^+3^) <= 15. This value is a 2.8 +/- 0.7 increase in {OMEGA}_C_^+3^ compared to the error-weighted mean from several 1 < z < 5 surveys for C IV absorbers. A simple linear regression to {OMEGA}_C_^+3^ over the age of the universe indicates that {OMEGA}_C_^+3^ has slowly but steadily increased from z = 5 --> 0, with d{OMEGA}_C_^+3^/ dt_age = (0.42 +/- 0.2) x 10^-8^ Gyr^-1^. Key words: intergalactic medium, quasars: absorption lines, techniques: spectroscopic
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