Simulations and Observations of Galaxies Constrained through Scaling Relations

Abstract

Understanding galaxy formation and evolution requires robust comparisons of observations and simulations of galaxies. This thesis contrasts rich observations of galaxies with simulations (hydrodynamical and semi-analytical models, hereafter SAMs1 ) to study structural galaxy scaling relations and star formation quenching. The role of AGN feedback on galaxy quenching is studied for central galaxies at z = 0 through the comparison of 500,000 SDSS galaxies with SAMs (L-GALAXIES and SAGE). We find that galaxy passive fractions measured for observations and the SAGE SAMs correlate with the stellar mass of the bulge component; for the L-GALAXIES SAMs, passive fractions correlate with halo and black hole mass. Overall, SAMs do not reproduce the observed passive fractions as they fail to model the coupling between the heating and cooling of gas due to AGN feedback. We also extract and compile a multi-band photometric and environmental catalogue for ∼8000 MaNGA galaxies. The deep surface brightness profiles are extracted in a non-parametric fashion from the automated software AUTOPROF and reach depths of 28.5 g − mag arcsec−2 , 27.8 r − mag arcsec−2 and 26.7 z − mag arcsec−2 . Non-parametric surface brightness profiles are shown to be more robust and reproducible relative to model (S´ersic or S´ersic + Exponential) dependent surface brightness profiles. As a complement to the photometric catalog, 1All acronyms are defined in the glossary. i rotation curves and a dynamical catalogue are also presented and used to construct multiple observed scaling relations. The latter are compared to similar scaling relations from the high-resolution NIHAO zoom-in simulations. NIHAO galaxies broadly agree with 12 observed scaling relations which the exception of those involved central surface densities (measured via Σ1). Finally, we have also compared simulated field and LG dwarf galaxies to highlight similarities and differences. Present-day LG dwarfs show similar stellar properties to field galaxies but very different gas properties, particularly hot gas metallicities. The difference in gas metal content is the result of interactions amongst LG dwarfs which live in a higher density environment than the field. The high quality data reductions presented in this thesis will lead to further refinement of the cosmological simulations.