COSMOS-Web: Star formation along the early Hubble sequence and the evolution of dust over the redshift range 0<z<12

Abstract We have carried out a stacking analysis with the COSMOS-Web catalogue on one of the deepest ever SCUBA-2 images at 850-μm, allowing us to estimate the mean submillimetre flux density for samples of galaxies split by stellar mass and morphological class over the redshift range 0 < z < 12. For all morphological classes, the mean star-formation rate estimated from the dust emission increases with redshift, reaching a value for the most massive galaxies ($\rm M_* \simeq 10^{11}\ {\rm M}_{\odot }$) of $\rm \gtrapprox 80\ {\rm M}_{\odot }\ yr^{-1}$ at 2 < z < 4.5. In this redshift range, the mean star-formation rate for these galaxies falls along the Hubble sequence from $\rm \simeq 280\ {\rm M}_{\odot }\ yr^{-1}$ for irregular galaxies at one end to $\rm \simeq 80\ {\rm M}_{\odot }\ yr^{-1}$for spheroids at the other end, which shows that quenching was already happening shortly after the emergence of the Hubble sequence. We also show that the transformation of ‘submillimetre galaxies’ can reproduce the growth in number-density of massive bulge-dominated and spheroidal galaxies over the redshift range 1.5 < z < 4. As a side-project, we have used our stacking results to determine the relationship between the mean density of dust and redshift in the range $\rm 0 < z <12$. We show that a chemical evolution model based on the ‘star-formation history’ of the universe, with a gas outflow rate equal to the star-formation rate, can explain the monotonic rise with redshift in the dust-to-stellar mass ratio and reproduce the relationship between mean dust density and redshift remarkably accurately.