Logo image
Back
Average Properties of a Large Sample of z_abs ~ z_em associated Mg II Absorption Line Systems
Journal article   Open access

Average Properties of a Large Sample of z_abs ~ z_em associated Mg II Absorption Line Systems

D. Vanden Berk, P Khare, D. G York, G. T Richards, B Lundgren, Y Alsayyad, V. P Kulkarni, M SubbaRao, D. P Schneider, T Heckman, …
25 Jan 2008
DOI: https://doi.org/10.1086/587122
url
https://doi.org/10.1086/587122View
Published, Version of Record (VoR) Open

Abstract

Physics - Cosmology and Nongalactic Astrophysics Physics - Earth and Planetary Astrophysics Physics - Instrumentation and Methods for Astrophysics Physics - High Energy Astrophysical Phenomena Physics - Solar and Stellar Astrophysics Physics - Astrophysics of Galaxies
Astrophys.J.679:239-259,2008 We have studied a sample of 415 associated (z_ab z_em; relative velocity with respect to QSO <3000km/s) Mg II absorption systems with 1.0<=z_ab<=1.86, in the spectra of SDSS DR3 QSOs, to determine the dust content and ionization state in the absorbers. We studied the dependence of these properties on the properties of the QSOs and also, compared the properties with those of a similarly selected sample of 809 intervening systems (apparent relative velocity with respect to the QSO of >3000km/s), so as to understand their origin. From the analysis of the composite spectra, as well as from the comparison of measured equivalent widths in individual spectra, we conclude that the associated Mg II absorbers have higher apparent ionization, measured by the strength of the C IV absorption lines compared to the Mg II absorption lines, than the intervening absorbers. The ionization so measured appears to be related to apparent ejection velocity, being lower as the apparent ejection velocity is more and more positive. There is clear evidence, from the composite spectra, for SMC like dust attenuation in these systems; the 2175AA absorption feature is not present. The extinction is almost twice that observed in the similarly selected sample of intervening systems. We reconfirm that QSOs with non-zero FIRST radio flux are intrinsically redder than the QSOs with no detection in the FIRST survey. The incidence of associated Mg II systems in QSOs with non-zero FIRST radio flux is 1.7 times that in the QSOs with no detection in the FIRST survey. The associated absorbers in radio-detected QSOs which comprise about 12% of our sample, cause 3 times more reddening than the associated absorbers in radio-undetected QSOs. This excess reddening possibly suggests an intrinsic nature for the associated absorbers in radio-detected QSOs.

Metrics

12 Record Views
40 citations in Web of Science
42 citations in Scopus

Details

InCites Highlights

Data related to this publication, from InCites Benchmarking & Analytics tool:

Collaboration types
Domestic collaboration
International collaboration
Web of Science research areas
Astronomy & Astrophysics
Logo image