An excess of damped Lyman alpha galaxies near QSOs

Abstract

We present a sample of 33 damped Lyman alpha systems (DLAs) discovered in the Sloan Digital Sky Survey (SDSS) whose absorption redshifts (z_abs) are within 6000 km/s of the QSO's 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 % complete for absorbers with N(HI) >= 2e20 cm^-2. The derived number density of DLAs per unit redshift, n(z), within v < 6000 km/s is higher (3.5 sigma 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.

arXiv commentAccepted for publication in MNRAS (13 pages, 6 figures)

References in corpus (33)

• Composite Quasar Spectra From the Sloan Digital Sky Survey
• The Third Data Release of the Sloan Digital Sky Survey
• Damped Lyman alpha Systems
• A Large Structure of Galaxies At Redshift z~3 and its Cosmological Implications
• The HIPASS catalogue: Omega_HI and environmental effects on the HI mass function of galaxies
• The SDSS Damped Lya Survey: Data Release 3
• Abundances at High Redshifts: the Chemical Enrichment History of Damped Lyman-alpha Galaxies
• Broad Emission Line Shifts in Quasars: An Orientation Measure for Radio-Quiet Quasars?
• The FIRST Bright Quasar Survey. II. 60 Nights and 1200 Spectra Later
• Discovery of Damped Lyman-Alpha Systems at Redshifts Less Than 1.65 and Results on their Incidence and Cosmological Mass Density
• Surveys for z > 3 Damped Lyman-alpha Absorption Systems
• Cosmic Evolution of Quasar Clustering: Implications for the Host Haloes
• The CORALS Survey I: New Estimates of the Number Density and Gas Content of Damped Lyman Alpha Systems Free from Dust Bias
• Keck High Resolution Spectroscopy of PKS 0123+257: Intrinsic Absorption in a Radio Loud Quasar
• Evidence for Primordial Clustering Around the QSO SDSS J1030+0524 at z=6.28
• Absorption Systems in the Spectra of 66 z > 4 Quasars
• The cluster environments of powerful radio-loud and radio-quiet AGN
• The SDSS Damped Lya Survey: Data Release 1
• The CORALS Survey II: Clues to Galaxy Clustering Around QSOs from z_abs ~ z_em Damped Lyman Alpha Systems
• An Optical/Near-Infrared Study of Radio-Loud Quasar Environments II. Imaging Results
• APM z>4 QSO Survey: Distribution and Evolution of High Column Density HI Absorbers
• Chemical abundances in quasar host galaxies and environments from narrow absorption line systems
• Radio-quiet quasar environments at 0.5 < z < 0.8
• Distinct Abundance Patterns in Multiple Damped Ly-alpha Galaxies: Evidence for Truncated Star Formation?
• Unusual Metal Abundances in a Pair of Damped Lyman Alpha Systems at z~2
• High-Redshift Superclustering of QSO Absorption Line Systems on 100 Mpc Scales
• An Optical/Near-Infrared Study of Radio-Loud Quasar Environments I. Methods and z=1-2 Observations
• Cluster of galaxies around seven radio-loud QSOs at 1<z<1.6: K-band images
• Clustering of red Galaxies near the Radio-loud Quasar 1335.8+2834 at z=1.1
• Double-Damped Lyman Alpha Absorption: A Possible Large Neutral Hydrogen Gas Filament Near Redshift z=1
• Large Scale Structure at z=1.2 Outlined by MgII Absorbers
• Detection of 20-30 Mpc-scale Galaxy Structures Embedded in 100 Mpc-scale Structures of Quasars and MgII Absorbers at z~0.8 and z~1.2
• Red Companions to a z=2.15 Radio Loud Quasar

Cited by in corpus (26)

• A High-Resolution Survey of Low-Redshift QSO Absorption Lines: Statistics and Physical Conditions of O VI Absorbers
• The Neutral Hydrogen Cosmological Mass Density at z=5
• A Definitive Survey for Lyman Limit Systems at z~3.5 with the Sloan Digital Sky Survey
• Quasars Probing Quasars I: Optically Thick Absorbers Near Luminous Quasars
• High-Redshift SDSS Quasars with Weak Emission Lines
• Quasars Probing Quasars II: The Anisotropic Clustering of Optically Thick Absorbers around Quasars
• Quasars Probing Quasars III: New Clues to Feedback, Quenching, and the Physics of Massive Galaxy Formation
• C IV absorption in damped and sub-damped Lyman-alpha systems: correlations with metallicity and implications for galactic winds at z~2-3
• The evolution of neutral gas in damped Lyman $\alpha$ systems from the XQ-100 survey
• The SDSS-DR5 Survey for Proximate Damped Lya Systems
• The nature of proximate damped Lyman alpha systems
• A z = 3 Lyman Alpha Blob Associated with a Damped Lyman Alpha System Proximate to its Background Quasar
• Galaxy Clusters in the Line of Sight to Background Quasars: I. Survey Design and Incidence of MgII Absorbers at Cluster Redshifts
• Chemical abundances of damped Lyman alpha systems in the XQ-100 survey
• Metal-Enriched Plasma in Protogalactic Halos: A Survey of N V Absorption in High-z Damped & Sub-Damped Lyman-alpha Systems
• Coincident, 100 kpc-scale damped Lyman alpha absorption towards a binary QSO: how large are galaxies at z ~ 3?
• HI content, metallicities and spin temperatures of damped and sub-damped Lyman alpha systems in the redshift desert (0.6 < z < 1.7)
• Metal Absorption Systems in Spectra of Pairs of QSOs
• Galaxy counterparts of intervening high-z sub-DLAs/DLAs and MgII absorbers towards gamma-ray bursts
• The Sightline to Q2343-BX415: Clues to Galaxy Formation in a Quasar Environment
• The large scale clustering of radio sources
• Metallicities and dust content of proximate damped Lyman alpha systems in the Sloan Digital Sky Survey
• A quasar hiding behind two dusty absorbers. Quantifying the selection bias of metal-rich, damped Lyman-alpha absorption systems
• A search for damped Lyman-alpha systems towards radio-loud quasars I: The optical survey
• Astrophysics in 2006
• High-ion absorption in the proximate damped Lyman-alpha system toward Q0841+129