Description
We use the deep imaging from the JWST PRIMER survey to study the properties of (sub)mm sources detected by ALMA in the centre of the COSMOS field, with the aim of better constraining the history of dust-enshrouded star formation. The wealth of ALMA data in this field enabled us to isolate a robust sample of 128 (sub)mm sources, spanning two decades in (sub)mm flux density. The JWST imaging is deep/red enough to reveal secure galaxy counterparts for all of these sources. Moreover, 52% of the galaxies have spectroscopic redshifts, enabling us to refine the photo-zs for the remaining galaxies. Armed with this robust redshift information, we calculate the star-formation rates (SFR) and stellar masses of all 128 ALMA-detected galaxies, and place them in the context of other galaxies in the field. We find that the vast majority of star formation is dust-enshrouded in the ALMA-detected galaxies, with SFR ranging from $\sim1000$ down to $\sim20\,\rm{M_{\odot}\,yr^{-1}}$. We also find that virtually all ($126/128$) have high stellar masses, at all redshifts, with $M_*>10^{10}\,\rm{M_{\odot}}$. The unusually high quality of our sample enables us to make a robust estimate of the contribution of the ALMA-detected galaxies to cosmic star-formation rate density (SFRD) from $z=2$ out to $z=7$. Finally, we use our knowledge of all other massive galaxies in the field to produce a completeness-corrected estimate of dust-enshrouded cosmic SFRD. This confirms that UV-visible star formation dominates at $z>4$, but also indicates that dust-enshrouded star formation likely still made a significant contribution at higher redshifts.
