The Dirt on Dry Mergers
Abstract
Using data from the Spitzer Space Telescope, we analyze the mid-infrared (3-70 μm) spectral energy distributions of dry merger candidates in the Boötes field of the NOAO Deep Wide-Field Survey. These candidates were selected by previous authors to be luminous, red, early-type galaxies with morphological evidence of recent tidal interactions. We find that a significant fraction of these candidates exhibit 8 and 24 μm excesses compared to expectations for old stellar populations. We estimate that a quarter of dry merger candidates have mid-infrared-derived star formation rates greater than ~1 M sun yr-1. This represents a "frosting" on top of a large old stellar population, and has been seen in previous studies of elliptical galaxies. Further, the dry merger candidates include a higher fraction of star-forming galaxies relative to a control sample without tidal features. We therefore conclude that the star formation in these massive ellipticals is likely triggered by merger activity. Our data suggest that the mergers responsible for the observed tidal features were not completely dry, and may be minor mergers involving a gas-rich dwarf galaxy.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 2011
- DOI:
- 10.1088/0004-637X/730/2/130
- arXiv:
- arXiv:1102.2929
- Bibcode:
- 2011ApJ...730..130D
- Keywords:
-
- galaxies: active;
- galaxies: evolution;
- galaxies: formation;
- infrared: galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- Accepted for publication in ApJ. Update includes small corrections that do not impact the science