Spheroidal Post-mergers In The Local Universe
Abstract
Galaxy merging is a fundamental aspect of the standard hierarchical galaxy formation paradigm. In Darg et al. (2010, MNRAS.401.1043) a large, homogeneous catalogue of mergers was compiled through direct visual inspection of the entire SDSS spectro- scopic sample using the Galaxy Zoo project. We explore a subset of galaxies from this catalogue that are spheroidal `post-mergers’ (SPMs) - where a single remnant is in the final stages of relaxation and shows evidence for a dominant bulge, making them plausible progenitors of early-type galaxies. The SPMs inhabit low-density environments and have bluer colours than the general early-type galaxy population due to merger-induced star formation. 68% of the SPMs exhibit emission-line activity, either as LINER or Seyfert-like emission, while the rest are classified as star forming (16%) or quiescent (26%). Comparison to the emission line activity in the Darg et al. sample - in which the mergers are still in progress - indicates that the AGN fraction rises in the post-mergers, suggesting that the AGN phase is dominant only in the very final stages the merging process. The optical colours of the SPMs and the plausible mass ratios for their progenitors indicate that, while a minority are consistent with major mergers between two early-type galaxies, the vast majority are remnants of major mergers where at least one progenitor is a late-type galaxy.
- Publication:
-
American Astronomical Society Meeting Abstracts #218
- Pub Date:
- May 2011
- Bibcode:
- 2011AAS...21820606C