Issue |
A&A
Volume 417, Number 2, April II 2004
|
|
---|---|---|
Page(s) | 443 - 450 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20034213 | |
Published online | 19 March 2004 |
CIV absorbers in z
quasars:
Tracing early galactic halos evolution*
1
Osservatorio Astronomico di Trieste, via Tiepolo, 11, 34131 Trieste, Italy
2
Institut d'Astrophysique de Paris, 98 bis Bld Arago, 75014 Paris, France
3
LERMA, Observatoire de Paris, 61 avenue de l'Observatoire, 75 014 Paris, France
4
Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK
Corresponding author: C. Péroux, peroux@ts.astro.it
Received:
20
August
2003
Accepted:
3
December
2003
We use 29 quasar spectra to build a homogeneous
sample of high-redshift CIV absorbers. We use these data to
calculate the number density,
, of
Å
CIV doublets. We find that
increases with time from
. In addition,
Å CIV systems
are more numerous than the former at all redshifts. On the contrary,
of Wrest(MgII)
Å MgII doublets decreases
with time, in agreement with results from studies of LLS number
densities. Below
, none of all the classes of absorbers show
signs of evolution. We interpret this as the formation of galactic
envelopes from smaller halos. Furthermore, the doublet ratio
/
is found to decrease with time, a
signature of the increase of the mean CIV column density. Finally,
the W(SiIV1393)/W(CIV1548) ratios in strong absorbers (
Å) is found to be approximately constant
from
to
and then to decrease with time. This result
suggests that the highest column density absorbers are not sensitive
to changes in the ionization continuum.
Key words: cosmology: observations / galaxies: evolution / galaxies: quasars: absorption lines / galaxies: halos / galaxies: high-redshift
© ESO, 2004
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