Herschel☆-ATLAS: properties of dusty massive galaxies at low and high redshifts

We present a comparison of the physical properties of a rest-frame 250-mu m-selected sample of massive, dusty galaxies from 0 < z < 5.3. Our sample comprises 29 high-redshift submillimetre galaxies (SMGs) from the literature and 843 dusty galaxies at z < 0.5 from the Herschel-Astrophysical TeraHertz Large Area Survey (H-ATLAS), selected to have a similar stellar mass to the SMGs. The z > 1 SMGs have an average star formation rate (SFR) of 390(-70)(+80) M-circle dot yr(-1), which is 120 times that of the low-redshift sample matched in stellar mass to the SMGs (SFR = 3.3 +/- 0.2 M-circle dot yr(-1)). The SMGs harbour a substantial mass of dust (1.2(-0.2)(+0.3) x 10(9) M-circle dot), compared to (1.6 +/- 0.1) x 10(8) M-circle dot for low-redshift dusty galaxies. At low redshifts, the dust luminosity is dominated by the diffuse interstellar medium, whereas a large fraction of the dust luminosity in SMGs originates from star-forming regions. At the same dust mass, SMGs are offset towards a higher SFR compared to the low-redshift H-ATLAS galaxies. This is not only due to the higher gas fraction in SMGs but also because they are undergoing a more efficient mode of star formation, which is consistent with their bursty star formation histories. The offset in SFR between SMGs and low-redshift galaxies is similar to that found in CO studies, suggesting that dust mass is as good a tracer of molecular gas as CO.