Herschel ⋆ - ATLAS : Properties of dusty massive galaxies at low and high redshifts

We present a comparison of the physical properties of a rest-frame 250μm selected sample of massive, dusty galaxies from 0 < z < 5.3. Our sample comprises 29 highredshift submillimetre galaxies (SMGs) from the literature, and 843 dusty galaxies at z < 0.5 from the Herschel -ATLAS, selected to have a similar stellar mass to the SMGs. The z > 1 SMGs have an average SFR of 390 −70M⊙yr −1 which is 120 times that of the low-redshift sample matched in stellar mass to the SMGs (SFR= 3.3± 0.2M⊙yr ). The SMGs harbour a substantial mass of dust (1.2 −0.2× 10 9 M⊙), compared to (1.6± 0.1)× 10 M⊙ for low-redshift dusty galaxies. At low redshifts the dust luminosity is dominated by the diffuse ISM, 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.