C IV absorbers in z >4 quasars: Tracing early galactic halos evolution

Céline Péroux (1) , Patrick Petitjean (2, 3) , B. Aracil (2) , Michael J. Irwin (4) , Richard G. Mcmahon (4)

1 INAF-OATs - INAF-Osservatorio Astronomico di Trieste
2 IAP - Institut d'Astrophysique de Paris
3 LERMA - Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique
4 IoA - Institute of Astronomy, University of Cambridge

We use 29 z>4 quasar spectra to build a homogeneous sample of high-redshift C IV absorbers. We use these data to calculate the number density, n(z), of W_rest(C IV)>0.30 Å C IV doublets. We find that n(z) increases with time from z˜4.5. In addition, W_rest(C IV)>0.15 Å C IV systems are more numerous than the former at all redshifts. On the contrary, n(z) of W_rest(Mg II)>0.30 Å Mg II doublets decreases with time, in agreement with results from studies of LLS number densities. Below z=0.50 Å) is found to be approximately constant from z=3.5 to z=2.5 and then to decrease with time. This result suggests that the highest column density absorbers are not sensitive to changes in the ionization continuum.

Domaines: Astrophysique [astro-ph]

Céline Péroux, Patrick Petitjean, B. Aracil, Michael J. Irwin, Richard G. Mcmahon. C IV absorbers in z >4 quasars: Tracing early galactic halos evolution. Astronomy and Astrophysics - A&A, 2004, 417, pp.443-450. ⟨10.1051/0004-6361:20034213⟩. ⟨hal-03786334⟩