Journal Article

The SCUBA Half Degree Extragalactic Survey (SHADES) – IX. The environment, mass and redshift dependence of star formation

S. Serjeant, S. Dye, A. Mortier, J. Peacock, E. Egami, M. Cirasuolo, G. Rieke, C. Borys, S. Chapman, D. Clements, K. Coppin, J. Dunlop, S. Eales, D. Farrah, M. Halpern, P. Mauskopf, A. Pope, M. Rowan-Robinson, D. Scott, I. Smail and M. Vaccari

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 386, issue 4, pages 1907-1921
Published in print June 2008 | ISSN: 0035-8711
Published online April 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13197.x
The SCUBA Half Degree Extragalactic Survey (SHADES) – IX. The environment, mass and redshift dependence of star formation

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We present a comparison between the SCUBA (Submillimetre Common User Bolometer Array) Half Degree Extragalactic Survey (SHADES) at 450 and 850 μm in the Lockman Hole East with a deep Spitzer Space Telescope survey at 3.6–24 μm 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 0.5–2 Mpc 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 <1011M, 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.

Keywords: galaxies: evolution; galaxies: formation; galaxies: starburst; cosmology: observations; infrared: galaxies; submillimetre

Journal Article.  8975 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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