2005/12/07 by David M. Russell, D. M. Russell, Sara L. Ellison +2 · 4 citations
Physics and Astronomy · #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2005.09964.x
published as Mon.Not.Roy.Astron.Soc.367:412-422,2006 · Accepted for publication in MNRAS (13 pages, 6 figures)
arxiv created 2005/12/07 · openalex publication_date 2006/01/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We present a sample of 33 damped Lyman α systems (DLAs) discovered in the Sloan Digital Sky Survey (SDSS) whose absorption redshifts (zabs) are within 6000 km s−1 of the quasi-stellar object's (QSO) systemic redshift (zsys). Our sample is based on 731 2.5 < zsys < 4.5 non-broad absorption line (non-BAL) QSOs from Data Release 3 (DR3) of the SDSS. We estimate that our search is ≈100 per cent complete for absorbers with N(H i) = 2 × 1020 cm−2. The derived number density of DLAs per unit redshift, n(z), within Δv < 6000 km s−1 is higher (3.5σ significance) by almost a factor of 2 than that of intervening absorbers observed in the SDSS DR3, i.e. there is evidence for an overdensity of galaxies near the QSOs. This provides a physical motivation for excluding DLAs at small velocity separations in surveys of intervening ‘field’ DLAs. In addition, we find that the overdensity of proximate DLAs is independent of the radio-loudness of the QSO, consistent with the environments of radio-loud and radio-quiet QSOs being similar.