The SCUBA Half Degree Extragalactic Survey (SHADES) - IX. The environment, mass and redshift dependence of star formation
Abstract
We present a comparison between the SCUBA (Submillimetre Common User Bolometer Array) Half Degree Extragalactic Survey (SHADES) at 450 and 850μm in the Lockman Hole East with a deep Spitzer Space Telescope survey at 3.6-24μm conducted in guaranteed time. Using stacking analyses we demonstrate a striking correspondence between the galaxies contributing the submm extragalactic background light, with those likely to dominate the backgrounds at Spitzer wavelengths. Using a combination BRIzK plus Spitzer photometric redshifts, we show that at least a third of the Spitzer-identified submm galaxies at 1 < z < 1.5 appear to reside in overdensities when the density field is smoothed at 0.5-2Mpc comoving diameters, supporting the high-redshift reversal of the local star formation-galaxy density relation. We derive the dust-shrouded cosmic star formation history of galaxies as a function of assembled stellar masses. For model stellar masses <1011Msolar, this peaks at lower redshifts than the ostensible z ~ 2.2 maximum for submm point sources, adding to the growing consensus for `downsizing' in star formation. Our surveys are also consistent with `downsizing' in mass assembly. Both the mean star formation rates <dM*/dt> and specific star formation rates <(1/M*) d M*/d t> are in striking disagreement with some semi-analytic predictions from the Millenium Simulation. The discrepancy could either be resolved with a top-heavy initial mass function, or a significant component of the submm flux heated by the interstellar radiation field.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- June 2008
- DOI:
- 10.1111/j.1365-2966.2008.13197.x
- arXiv:
- arXiv:0712.3613
- Bibcode:
- 2008MNRAS.386.1907S
- Keywords:
-
- galaxies: evolution;
- galaxies: formation;
- galaxies: starburst;
- cosmology: observations;
- infrared: galaxies;
- submillimetre;
- Astrophysics
- E-Print:
- Accepted by MNRAS. SMG environments analysis extended. 17 pages, 18 figures. Includes BoxedEPS