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Constraints on the Universal CIV Mass Density at z~6 from Early IR Spectra Obtained with the Magellan FIRE Spectrograph

, , , , , , , , , , , and .
(2011)cite arxiv:1104.4117 Comment: 14 pages, 6 figures, 2 tables. Submitted to ApJ.

Abstract

We present a new determination of the intergalactic CIV mass density at 4.3 < z < 6.3. Our constraints are derived from high signal-to-noise spectra of seven quasars at z > 5.8 obtained with the newly commissioned FIRE spectrograph on the Magellan Baade telescope, coupled with six observations of northern objects taken from the literature. We confirm the presence of a downturn in the CIV abundance at <z>=5.66 by a factor of 4.1 relative to its value at <z>=4.96, as measured in the same sightlines. In the FIRE sample, a strong system previously reported in the literature as CIV at z=5.82 is re-identified as MgII at z=2.78, leading to a substantial downward revision in $Ømega_CIV$ for these prior studies. Additionally we confirm the presence of at least two systems with low-ionization CII, SiII, and OI absorption but relatively weak signal from CIV. The latter systems systems may be of interest if the downward trend in $Ømega_CIV$ at high redshift is driven in part by ionization effects.

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