The assembly of dusty galaxies at $z \geq 4$: the build-up of stellar mass and its scaling relations with hints from early JWST data

The increasing number of distant galaxies observed with ALMA by the ALPINE and REBELS surveys, and the early release observations of the James Webb Space Telescope (JWST) promise to revolutionize our understanding of cosmic star formation and the assembly of normal, dusty galaxies. Here we introduce a new suite of cosmological simulations performed with \texttt{dustyGadget} to interpret high-redshift data. We investigate the comoving star formation history, the stellar mass density and a number of galaxy scaling relations such as the galaxy main sequence (MS), the stellar-to-halo mass and dust-to-stellar mass relations at $z > 4$. The predicted star formation rate and total stellar mass density rapidly increase in time with a remarkable agreement with available observations, including recent JWST ERO and DD-ERS data at $z \geq 8$. A well defined galaxy MS is found already at $z < 10$ following a non evolving power-law, in agreement with both JWST and REBELS data at the low/high-mass end respectively, and consistent with a star formation efficiently sustained by gas accretion and a specific star formation rate increasing with redshift, as established by recent observations. A population of low-mass galaxies ($\rm{Log(M_\star/M_\odot)} < 9$) at $z \leq 7$ exceeding present estimates in the stellar mass function is also responsible of a large scatter in the stellar-to-halo and dust-to-stellar mass relations. Future JWST observations will provide invaluable constraints on these low-mass galaxies, helping to shed light on their role in cosmic evolution....