Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2011-08-09
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
13 pages, 11 figures, 6 tables; online data included in electronic version as 1 FITS table and 2 machine readable tables; to b
Scientific paper
The aim of this project is to identify low-redshift host galaxies of quasar absorption-line systems by selecting galaxies which are seen in projection onto quasar sightlines. To this end, we use the Seventh Data Release of the Sloan Digital Sky Survey (SDSS-DR7) to construct a parent sample of 97489 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 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 (>=3.0 sigma), the Local Standard of Rest velocity along the sightline (>= 345 km/s), and the ratio of the impact parameter to the galaxy optical radius (<=5.0), we identify 4 absorption line systems that are associated with low-redshift galaxies at high confidence, consisting of two Ca II systems (one of which also shows Na I), and two Na I systems. These 4 systems arise in blue, L_r^* galaxies. Tables of the 108 absorption systems are provided to facilitate future follow up.
Cherinka Brian
Schulte-Ladbeck Regina E.
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