Specific star formation and the relation to stellar mass from 0 < z < 2 as seen in the far-infrared at 70 and 160 μm

Abstract

We use the Spitzer Wide-area InfraRed Extragalactic Legacy Survey (SWIRE) to explore the specific star formation activity of galaxies and their evolution near the peak of the cosmic far-infrared (FIR) background at 70 and 160 μm. We use a stacking analysis to determine the mean FIR properties of well-defined subsets of galaxies at flux levels well below the FIR catalogue detection limits of SWIRE and other Spitzer surveys. We tabulate the contribution of different subsets of galaxies to the FIR background at 70 and 160 μm. These long wavelengths provide a good constraint on the bolometric obscured emission. The large area provides good constraints at low z and in finer redshift bins than previous work. At all redshifts we find that the specific FIR luminosity decreases with increasing mass, following a trend LFIR/M* ∝ Mβ* with β = -0.38 ± 0.14. This is a more continuous change than expected from the De Lucia and Blaizot semi-analytic model suggesting modifications to the feedback prescriptions. We see an increase in the specific FIR luminosity by about a factor of ∼100 from 0 < z < 2 and find that the specific FIR luminosity evolves as (1 + z)α with α = 4.4 ± 0.3 for galaxies with 10.5