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|a Cooksey, Kathy
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|a MIT Kavli Institute for Astrophysics and Space Research
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|a Cooksey, Kathy
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|a Thom, Christopher
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|a Prochaska, J. Xavier
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|a Chen, Hsiao-Wen
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|a THE LAST EIGHT-BILLION YEARS OF INTERGALACTIC C IV EVOLUTION
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|b Institute of Physics/American Astronomical Society,
|c 2015-03-26T15:57:11Z.
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|z Get fulltext
|u http://hdl.handle.net/1721.1/96201
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|a 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 $\ge 3\sigma _{W_{r}}$. 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 ${d}\mathcal {N}_{\mathrm{C\,IV}}/{d}X= 4.1^{+0.7}_{-0.6}$ for log N(C+3) ≥ 13.2, and ${d}\mathcal {N}_{\mathrm{C\,IV}}/{d}X$ has not evolved significantly since z = 5. The best-fit power law to the G = 1 frequency distribution of column densities $f(N(\mathrm{C}^{+3})) \equiv k(N(\mathrm{C}^{+3})/N_{0})^{\alpha _{N}}$ has coefficient k = 0.67+0.18 -0.16 × 10-14 cm2 and exponent α N = -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: $\Omega _{\mathrm{C}^{+3}}= (6.20^{+1.82}_{-1.52}) \times 10^{-8}$ for 13 ≤ log N(C+3) ≤ 15. This value is a 2.8 ± 0.7 increase in $\Omega _{\mathrm{C}^{+3}}$ compared to the error-weighted mean from several 1 < z < 5 surveys for C IV absorbers. A simple linear regression to $\Omega _{\mathrm{C}^{+3}}$ over the age of the universe indicates that $\Omega _{\mathrm{C}^{+3}}$ has slowly but steadily increased from z = 5 → 0, with ${d}\Omega _{\mathrm{C}^{+3}}/ {d}t_{\rm age} = (0.42\pm 0.2)\times 10^{-8}\,{\rm Gyr}^{-1}$.
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|a Space Telescope Science Institute (U.S.) (HST archival grant 10679)
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|a National Science Foundation (U.S.) (NSF CAREER grant AST 05_48180)
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|a United States. National Aeronautics and Space Administration (NASA contract NAS 5-2655)
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|a Article
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|t Astrophysical Journal
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