Investigating lensing by absorbers in the 2dF-Quasar survey

Abstract

We use the first data release of the 2-degree Field Quasar survey to investigate the effect of gravitational magnification by foreground absorbing systems on background quasars. We select two populations of quasars from this sample: one with strong MgII/FeII absorbers and one without. The selection is done in such a way that the two populations have the same redshift distribution and the absorber detection procedure discards possible biases with quasar magnitude. We then compare their magnitude distributions and find a relative excess of bright quasars with absorbers. This effect is detected at the 2.4, 3.7 and 4.4 sigma levels in u-, b- and r-bands. Various explanations of the observed phenomenon are considered and several lines of evidence point towards gravitational lensing causing some of the differences observed in the magnitude distributions. We note that physical quasar-absorber associations may contribute to some extent to the observed correlations for low quasar-absorber velocity differences. We discuss the implications of these findings and propose future work which will allow us to strengthen and extend the results presented here.

arXiv comment13 pages, 9 figures, accepted for publication in Astronomy & Astrophysics

References in corpus (21)

• The Sloan Digital Sky Survey: Technical Summary
• The 2dF QSO Redshift Survey - I. The Optical QSO Luminosity Function
• Probing the Universe with Weak Lensing
• Mapping Cluster Mass Distributions via Gravitational Lensing of Background Galaxies
• Discovery of Damped Lyman-Alpha Systems at Redshifts Less Than 1.65 and Results on their Incidence and Cosmological Mass Density
• Field Galaxy Evolution Since Z~1 from a Sample of QSO Absorption-Selected Galaxies
• Surveys for z > 3 Damped Lyman-alpha Absorption Systems
• The 2dF QSO Redshift Survey - V. The 10k catalogue
• Evolution of Neutral Gas at High Redshift -- Implications for the Epoch of Galaxy Formation
• The Population of Weak Mg II Absorbers I. A Survey of 26 QSO HIRES/Keck Spectra
• Gaseous Galactic Halos and QSO Absorption Line Systems
• The CORALS Survey II: Clues to Galaxy Clustering Around QSOs from z_abs ~ z_em Damped Lyman Alpha Systems
• Determining the Fraction of Intrinsic CIV Absorption in Quasi-Stellar Object Absorption Line Systems
• Intrinsic Absorption in Radio-Selected QSOs
• GRAVITATIONAL LENSING OF QUASARS BY THEIR DAMPED LYMAN-ALPHA ABSORBERS
• The 2dF QSO Redshift Survey - IV. The QSO Power Spectrum from the 10k Catalogue
• An Excess of C IV Absorbers in Luminous QSOs: Evidence for Gravitational Lensing?
• Quasar Absorption Lines as a Function of Quasar Orientation Measures
• Effects of Dust on Gravitational Lensing by Spiral Galaxies
• The 2dF QSO Redshift Survey - VIII. Absorption systems in the 10k catalogue
• Lensing by Lyman Limit Systems: Determining the Mass to Gas Ratio

Cited by in corpus (16)

• Weak Gravitational Lensing
• Multi-Phase Galaxy Formation: High Velocity Clouds and the Missing Baryon Problem
• Gravitational Lensing
• Lensing, reddening and extinction effects of MgII absorbers from z=0.4 to z=2
• Dust-reddening and gravitational lensing of SDSS QSOs due to foreground damped Lyman-alpha systems
• A Cross-Correlation Analysis of Mg II Absorption Line Systems and Luminous Red Galaxies from the SDSS DR5
• Discovery of a z=6.1 Radio-Loud Quasar in the NDWFS
• The dust obscuration bias in Damped Lyman alpha systems
• The Number Density of 0.6 < z < 1.7 MgII Systems from CORALS: Observational Biases at Intermediate Redshift
• ALMACAL VI: Molecular gas mass density across cosmic time via a blind search for intervening molecular absorbers
• Clumpiness of Observed and Simulated Cold Circumgalactic Gas
• Weak Lensing of Baryon Acoustic Oscillations
• Quasar 2175 Å dust absorbers II: Correlation analysis and relationship with other absorption line systems
• Detecting and interpreting statistical lensing by absorbers
• Tracing the 10${}^7$K Warm-Hot Intergalactic Medium with UV absorption lines
• Gravitational Lensing as Signal and Noise in Lyman-alpha Forest Measurements