Star formation and stellar mass assembly in galaxy formation models

Abstract

We use the semi-analytic galaxy formation model, GALFORM, to explore the implications of results from multi-wavelength galaxy
surveys within the context of the hierarchical structure formation paradigm. Specific topics which we investigate include (i): the
biases that can be introduced by using spectral energy distribution fitting to infer stellar masses from broad-band photometry,
(ii) the reasons why galaxy formation models struggle to reproduce the exponential drop with time in star formation rates of star-forming galaxies
inferred from a wide range of observations, (iii) the physical processes that control the evolution in the median relationship between stellar mass
and halo mass predicted by galaxy formation models. We show that stellar masses of compact dusty star-forming galaxies could be
underestimated by SED fitting as a result of assuming a uniform foreground dust screen geometry. We explain how the standard implementation
of supernova feedback and gas reincorporation within galaxy formation models results in flat predicted star formation histories for
star forming galaxies. We show that this is inconsistent with observational data which imply that these star formation histories should
instead be peaked at intermediate redshift. We also show how the supernova feedback and gas reincorporation implementations within
standard galaxy formation models result in a baryon conversion efficiency within haloes that is roughly independent of cosmic time at fixed halo mass.
Consequently, the median stellar mass versus halo mass relationship is predicted by these models to not evolve significantly.