Volume 390, Number 1, July IV 2002
|Page(s)||13 - 25|
|Published online||05 July 2002|
High matter density peaks from UVES observations of QSO pairs: Correlation properties and chemical abundances*
Institut d'Astrophysique de Paris, 98bis Boulevard Arago, 75014 Paris, France
2 LERMA, Observatoire de Paris, 61 Av. de l'Observatoire, 75014 Paris, France
3 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany
4 Osservatorio Astronomico di Trieste, via G.B. Tiepolo, 11, 34131 Trieste, Italy
Corresponding author: V. D'Odorico, email@example.com
Accepted: 15 May 2002
We study the transverse clustering properties of high matter density peaks as traced by high column density absorption systems (either Lyman limit systems characterized by cm-2 or systems with Å) at redshifts between 2 and 3 with UVES spectra of two QSO pairs (UM680/UM681 at 56 arcsec angular separation and Q2344+1228/Q2343+1232 at 5 arcmin angular separation) and a QSO triplet (Q2139-4433/Q2139-4434/Q2138-4427 at 1, 7 and 8 arcmin angular separation). We find 3 damped Lyman-α systems ( cm-2): 2 coinciding with strong metal systems in the nearby line of sight and 1 matching the emission redshift of the paired QSO; plus 7 Lyman limit systems: 4 forming two matching couples and 3 without a corresponding metal system within ~3000 km s-1in the coupled line of sight. In summary, we detect five out of ten matching systems within 1000 km s-1, indicating a highly significant overdensity of strong absorption systems over separation lengths from ~1 to 8 h-1 Mpc. The observed coincidences could arise in gas due to starburst-driven superwinds associated with a quasar or a galaxy, or gas belonging to large scale structures like filaments or sheets. We also determine chemical abundance ratios for three damped Lyman-α systems. In particular, for the damped system at in the spectrum of Q2344+1228, new estimates of the ratios O/Fe, C/Fe are obtained: , . They indicate that O and C are not over-solar in this system.
Key words: galaxies: abundances / galaxies: high-redshift / quasars: absorption lines / cosmology: observations
© ESO, 2002
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