Tracking the chemical history of the Universe: the density of CIV at z~6

Abstract

Spectroscopy of high redshift (z) quasars (QSOs) has revealed the existence of absorption lines produced by metals in the line of sight to the QSO. The signature of carbon can be followed to very early cosmic times, showing that metals already exist in the intergalactic medium only ~ 1 Gyr after the Big Bang. In this work, we search for C iv absorption systems at z > 5 in seven QSO lines-of-sight not included in other studies. We determine the C iv comoving mass density (\Omega(CIV)), which is an integral measure of the amount of metals and ionizing photons emitted by previous generations of stars, and find that our current result is consistent with a rapid drop of intergalactic CIV at z > 5.