Open AccessAn excess of damped Lyman α galaxies near quasi‐stellar objects
Author(s) -
Russell David M.,
Ellison Sara L.,
Benn Chris R.
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2005.09964.x
Subject(s) - qsos , physics , astrophysics , redshift , galaxy , sky , astronomy , quasar , young stellar object , star formation
We present a sample of 33 damped Lyman α systems (DLAs) discovered in the Sloan Digital Sky Survey (SDSS) whose absorption redshifts ( z abs ) are within 6000 km s −1 of the quasi‐stellar object's (QSO) systemic redshift ( z sys ). Our sample is based on 731 2.5 < z sys < 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 × 10 20 cm −2 . The derived number density of DLAs per unit redshift, n ( z ), within Δ v < 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.