Modelling galaxies in the high redshift universe
This thesis describes the combination of a phenomenological model of galaxy formation with the spectrophotometric dust extinction model of Silva et al.(1998). I use TV-body simulations to predict the underlying dark matter density field in a hierarchal Lambda Cold Dark Matter universe. Analytic prescriptions of gas cooling, star formation and stellar feedback describes the formation and evolution of galaxies embedded in the hierarchy of dark matter haloes. Starlight is attenuated by a two-phase medium of graphite and silicate dust grains, yielding the observed spectral energy distribution of a galaxy from the UV to the submillimetre. With this in place, the role of dust in galaxy formation can be probed and assessed in a self-consistent manner, improving on the common plane-parallel slab and tunable dust temperature approach employed in many semi-analytic models.I first present model predictions of the local universe, demanding that an acceptable model must first perform well at z —0 before being tested at high redshift. I can adequately reproduce many key local observational constraints, although a few stimulating discrepancies are present. Not only will this ground the models in reality, it will then help assess whether a ‘standard* semi-analytic model can reproduce facets of the high redshift universe without recourse to new physics.I then use the above framework to present predictions at early times, where dust is known to play an important role in influencing the observed magnitudes, colours and properties of galaxies. Two further models are introduced to assess how different parameter choices that give similar local results diverge at early times. I first concentrate on the more global, well understood facets of the high redshift universe, namely the galaxy and stellar luminosity functions. I then construct mock surveys in an attempt to account for Lyman Break Galaxies (LBGs) at 2 = 3, of which there is a comprehensive array of high quality data available in the literature. Properties of LBGs can be adequately reproduced by the models, although there is a marked overabundance of such objects present, likely due to an underestimate of the dust extinction inherent in such objects.I finally use the mock survey approach to study Extremely Red Objects (EROs), galaxies with (R — K ) > 5 uncovered in deep K-band surveys, and Submillimetre Galaxies (SMGs) detected in blank field SCUBA surveys. These extreme objects tend to the bane of semi-analytic models, and I find that my model fares no different in this respect: a truncation method used to prevent the formation of overly massive galaxies at low redshift also inhibits their formation at early times. I severely underpredict the number counts of EROs and SMGs, although a few of their observational properties can be matched reasonably well. I then investigate the overlaps between distinct populations, and the fate of high redshift objects is followed through time, shedding light on relationships between evolutionary phases of galaxies.