Mathematics – Logic
Scientific paper
Mar 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005pgqa.conf..375p&link_type=abstract
Probing Galaxies through Quasar Absorption Lines, IAU Colloquium Proceedings of the International Astronomical Union 199, held M
Mathematics
Logic
Scientific paper
Absorbers seen in the spectrum of background quasars are a unique tool to select hi-rich galaxies at all redshifts. These allow us to determine the cosmological evolution of H I gas, ωhi+heii, a possible indicator of gas consumption as star formation proceeds. The damped Lyman-α systems (dlas with nhi ≥ 1020.3 cm-2) in particular are believed to contain a large fraction of the H I gas, but there are also indications that lower column density systems, namely "sub-damped Lyman-α" systems play a role at high-redshift. Here we present the discovery of high-redshift sub-dlas based on 17 z>4 quasar spectra observed with the ultraviolet-visual echelle spectrograph (UVES) on VLT. This sample is composed of 21 new sub-dlas which, together with another 10 systems from previous ESO archive studies, make up a homogeneous sample. The redshift evolution of the number density of several classes of absorbers is derived and shows that all systems seem to be evolving in the redshift range from z=5 to z˜3. The redshift evolution of the column density distribution, f(n,z), down to nhi=1019 cm-2 is also presented. A departure from a power law due to a flattening of f(n,z) in the sub-dla regime is present in the data. F(n,z) is further used to determine the H I gas mass contained in sub-dlas at z>2. The complete sample shows that sub-dlas are important at all redshifts from z=5 to z=2.
D'Odorico Sandro
Dessauges-Zavadsky Miroslava
Kim Tae Sun
McMahon Richard G.
Peroux Celine
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