Ca II and Na i quasar absorption-line systems in an emission-selected sample of SDSS DR7 galaxy/quasar projections. I. Sample selection

  • Cherinka B
  • Schulte-Ladbeck R
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The aim of this project is to identify low-redshift host galaxies of quasar absorption-line systems by selecting galaxies that are seen in projection onto quasar sightlines. To this end, we use the Seventh Data Release of the Sloan Digital Sky Survey to construct a parent sample of 97,489 galaxy/quasar projections at impact parameters of up to 100 kpc to the foreground galaxy. We then search the quasar spectra for absorption-line systems of Ca II and Na I within ±500 km s–1 of the galaxy's velocity. This yields 92 Ca II and 16 Na I absorption systems. We find that most of the Ca II and Na I systems are sightlines through the Galactic disk, through high-velocity cloud complexes in our halo, or Virgo Cluster sightlines. Placing constraints on the absorption line rest equivalent width significance (>=3.0σ), the local standard of rest velocity along the sightline (>=345 km s–1), and the ratio of the impact parameter to the galaxy optical radius (

Author-supplied keywords

  • catalogs
  • galaxies: general
  • quasars: absorption lines
  • quasars: individual (Ca ii, Nai)

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  • B. Cherinka

  • R. E. Schulte-Ladbeck

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