The Structures and Total (Minor + Major) Merger Histories of Massive Galaxies up to z ~ 3 in the HST GOODS NICMOS Survey: A Possible Solution to the Size Evolution Problem
Abstract
We investigate the total major (>1:4 by stellar mass) and minor (>1:100 by stellar mass) merger history of a population of 80 massive (M * > 1011 M ⊙) galaxies at high redshifts (z = 1.7-3). We utilize extremely deep and high-resolution Hubble Space Telescope H-band imaging from the GOODS NICMOS Survey, which corresponds to rest-frame optical wavelengths at the redshifts probed. We find that massive galaxies at high redshifts are often morphologically disturbed, with a CAS (concentration, C; asymmetry, A; clumpiness, S) deduced merger fraction fm = 0.23 ± 0.05 at z = 1.7-3. We find close accord between close pair methods (within 30 kpc apertures) and CAS methods for deducing major merger fractions at all redshifts. We deduce the total (minor + major) merger history of massive galaxies with M * > 109 M ⊙ galaxies, and find that this scales roughly linearly with log-stellar-mass and magnitude range. We test our close pair methods by utilizing mock galaxy catalogs from the Millennium Simulation. We compute the total number of mergers to be (4.5 ± 2.9)/langτ m rang from z = 3 to the present, to a stellar mass sensitivity threshold of ~1:100 (where τ m is the merger timescale in Gyr which varies as a function of mass). This corresponds to an average mass increase of (3.4 ± 2.2) × 1011 M ⊙ over the past 11.5 Gyr due to merging. We show that the size evolution observed for these galaxies may be mostly explained by this merging.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 2012
- DOI:
- 10.1088/0004-637X/747/1/34
- arXiv:
- arXiv:1111.5662
- Bibcode:
- 2012ApJ...747...34B
- Keywords:
-
- galaxies: evolution;
- galaxies: formation;
- galaxies: high-redshift;
- galaxies: interactions;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 19 pages, 10 figures, re-submitted to ApJ after a positive referee report, originally submitted on Sept 20 2011