C IV absorbers in z >4 quasars: Tracing early galactic halos evolution
Résumé
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 Wrest(C IV)>0.30 Å C IV doublets. We find that n(z) increases with time from z˜4.5. In addition, Wrest(C IV)>0.15 Å C IV systems are more numerous than the former at all redshifts. On the contrary, n(z) of Wrest(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]
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