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 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, 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 main sequence is found already at $z < 10$ following a non evolving power-law, which - if extrapolated at high-mass end - is in agreement with JWST, REBELS, and ALPINE data. This is 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 ($8 < \rm{Log(M_\star/M_\odot)} < 9$) at $z \leq 6 - 7$ that exceeds some of the current estimates of the stellar mass function is also at the origin of the scatter in the stellar-to-halo mass relation. Future JWST observations will provide invaluable constraints on these low-mass galaxies, helping to shed light on their role in cosmic evolution.