SHINING LIGHT ON MERGING GALAXIES. I. THE ONGOING MERGER OF A QUASAR WITH A 'GREEN VALLEY' GALAXY
- Department of Astronomy and Astrophysics, UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)
- Space Telescope Science Institute, 3200 San Martin Dr., Baltimore, MD 21218 (United States)
- Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003-9305 (United States)
Serendipitous observations of a pair z = 0.37 interacting galaxies (one hosting a quasar) show a massive gaseous bridge of material connecting the two objects. This bridge is photoionized by the quasar (QSO), revealing gas along the entire projected 38 h{sup -1}{sub 70} kpc sightline connecting the two galaxies. The emission lines that result give an unprecedented opportunity to study the merger process at this redshift. We determine the kinematics, ionization parameter (log U {approx} -2.5 {+-} 0.03), column density (N{sub H,perpendicular} {approx} 10{sup 21} cm{sup -2}), metallicity ([M/H] {approx} - 0.20 {+-} 0.15), and mass ({approx}10{sup 8} M{sub sun}) of the gaseous bridge. We simultaneously constrain properties of the QSO host (M{sub DM} > 8.8 x 10{sup 11} M{sub sun}) and its companion galaxy (M{sub DM} > 2.1 x 10{sup 11} M{sub sun}; M{sub *} {approx} 2 x 10{sup 10} M{sub sun}; stellar burst age = 300-800 Myr; SFR {approx}6 M{sub sun} yr{sup -1}; and metallicity 12 + log (O/H) = 8.64 {+-} 0.2). The general properties of this system match the standard paradigm of a galaxy-galaxy merger caught between first and second passages while one of the galaxies hosts an active quasar. The companion galaxy lies in the so-called green valley, with a stellar population consistent with a recent starburst triggered during the first passage of the merger and has no discernible active galactic nucleus activity. In addition to providing case studies of quasars associated with galaxy mergers, quasar/galaxy pairs with QSO-photoionized tidal bridges such as this one offer unique insights into the galaxy properties while also distinguishing an important and inadequately understood phase of galaxy evolution.
- OSTI ID:
- 21576519
- Journal Information:
- Astrophysical Journal, Vol. 735, Issue 1; Other Information: DOI: 10.1088/0004-637X/735/1/54; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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