The Star Formation Histories of z ~ 2 Dust-obscured Galaxies and Submillimeter-selected Galaxies
Abstract
The Spitzer Space Telescope has identified a population of ultraluminous infrared galaxies (ULIRGs) at z ~ 2 that may play an important role in the evolution of massive galaxies. We measure the stellar masses (M *) of two populations of Spitzer-selected ULIRGs that have extremely red R - [24] colors (dust-obscured galaxies, or DOGs) and compare our results with submillimeter-selected galaxies (SMGs). One set of 39 DOGs has a local maximum in their mid-infrared (mid-IR) spectral energy distribution (SED) at rest frame 1.6 μm associated with stellar emission ("bump DOGs"), while the other set of 51 DOGs have power-law mid-IR SEDs that are typical of obscured active galactic nuclei ("power-law DOGs"). We measure M * by applying Charlot & Bruzual stellar population synthesis models to broadband photometry in the rest-frame ultraviolet, optical, and near-infrared of each of these populations. Assuming a simple stellar population and a Chabrier initial mass function, we find that power-law DOGs and bump DOGs are on average a factor of 2 and 1.5 more massive than SMGs, respectively (median and inter-quartile M * values for SMGs, bump DOGs, and power-law DOGs are log(M */M ⊙) = 10.42+0.42 - 0.36, 10.62+0.36 - 0.32, and 10.71+0.40 - 0.34, respectively). More realistic star formation histories drawn from two competing theories for the nature of ULIRGs at z ~ 2 (major merger versus smooth accretion) can increase these mass estimates by up to 0.5 dex. A comparison of our stellar masses with the instantaneous star formation rate (SFR) in these z ~ 2 ULIRGs provides a preliminary indication supporting high SFRs for a given M *, a situation that arises more naturally in major mergers than in smooth accretion-powered systems.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 2012
- DOI:
- 10.1088/0004-637X/744/2/150
- arXiv:
- arXiv:1111.2869
- Bibcode:
- 2012ApJ...744..150B
- Keywords:
-
- galaxies: evolution;
- galaxies: fundamental parameters;
- galaxies: high-redshift;
- galaxies: stellar content;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 17 pages, 7 figures, 3 tables. Plus figures showing SEDs and best-fit synthesized stellar population model. Accepted to the ApJ