Shape asymmetry: a morphological indicator for automatic detection of galaxies in the post-coalescence merger stages
Abstract
We present a new morphological indicator designed for automated recognition of galaxies with faint asymmetric tidal features suggestive of an ongoing or past merger. We use the new indicator, together with pre-existing diagnostics of galaxy structure to study the role of galaxy mergers in inducing (post-) starburst spectral signatures in local galaxies, and investigate whether (post-) starburst galaxies play a role in the build-up of the `red sequence'. Our morphological and structural analysis of an evolutionary sample of 335 (post-) starburst galaxies in the Sloan Digital Sky Survey DR7 with starburst ages 0 < tSB < 0.6 Gyr, shows that 45 per cent of galaxies with young starbursts (tSB < 0.1 Gyr) show signatures of an ongoing or past merger. This fraction declines with starburst age, and we find a good agreement between automated and visual classifications. The majority of the oldest (post-) starburst galaxies in our sample (tSB ∼ 0.6 Gyr) have structural properties characteristic of early-type discs and are not as highly concentrated as the fully quenched galaxies commonly found on the `red sequence' in the present day Universe. This suggests that, if (post-) starburst galaxies are a transition phase between active star-formation and quiescence, they do not attain the structure of presently quenched galaxies within the first 0.6 Gyr after the starburst.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- March 2016
- DOI:
- 10.1093/mnras/stv2878
- arXiv:
- arXiv:1512.02000
- Bibcode:
- 2016MNRAS.456.3032P
- Keywords:
-
- galaxies: evolution;
- galaxies: interactions;
- galaxies: starburst;
- galaxies: structure;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Instrumentation and Methods for Astrophysics
- E-Print:
- Accepted for publication in MNRAS, 20 pages, 13 figures