Galactic nebular lines in the fibre spectra of background QSOs: Reaching a hundred QSO-galaxy pairs with spectroscopic and photometric measurements

Lorrie A. Straka, Pasquier Noterdaeme, Raghunathan Srianand, Songkiat Nutalaya, Varsha P. Kulkarni, Pushpa Khare, David Bowen, Michael Bishof, Donald G. York

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


We present photometric and spectroscopic measurements of 53 QSO-galaxy pairs from the Sloan Digital Sky Survey (SDSS),where nebular emission lines from a 0 < z < 0.84 foreground galaxy are detected in the fibre spectra of a background QSO, bringing the overall sample to 103 QSO-galaxy pairs detected in the SDSS. We here study the nature of these systems. Detected foreground galaxies appear at impact parameters between 0.37 and 12.68 kpc. The presence of oxygen and Balmer emission lines allows us to determine the emission linemetallicities for our sample, which are on average supersolar in value. Star formation rates for our sample are in the range 0.01-12 M yr-1. We utilize photometric redshift fitting techniques to estimate the M* values of our galaxies (log M* =7.34-11.54), and extrapolate this relationship to those galaxies with no imaging detections.Where available, we measure the absorption features present in the QSO spectrum due to the foreground galaxy and the relationships between their rest equivalent widths. We report an anticorrelation between impact parameter and E(B - V)(g - i), as well as a correlation between galaxy colour (u - r) and E(B - V)(g - i). We find that our sample is one of late-type, star-forming galaxies comparable to field galaxies in a similar redshift range, providing important clues to better understand absorption systems. These galaxies represent a sample of typical galaxies in the local Universe for which abundances, extinction, morphology, and absorption properties may be measured using background QSOs with great potential for follow-up observations.

Original languageEnglish (US)
Pages (from-to)3856-3872
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - Mar 11 2015

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Cosmology: observations
  • Galaxies: evolution
  • Galaxies: photometry
  • Quasars: absorption lines


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