Calibrating Mass Modeling Methods with Numerical Simulations of Galaxies

Abstract

Studying and modeling the distribution of baryons in galaxies plays a crucial role in our understanding of the dark matter (DM) distribution in those galaxies. However, as we lack access to the true distribution of baryons in observed galaxies, the uncertainties associated with models can only be approximated. In this thesis, we use zoom-in cosmological hydrodynamical simulations to investigate the errors associated with assumptions in galaxy mass models. We take advantage of the NIHAO (Numerical Investigation of a Hundred Astrophysical Objects) simulations suite to test commonly-used mass model prescriptions. Our study is restricted to disk galaxies (as gauged by the flattening of their stellar distribution). Overall, NIHAO successfully produces realistic flattened stellar disks; however, the gas distribution is puffed up compared to observations. Thanks to our complete knowledge of the mass distribution of each galaxy component, we can extract the rotation curves (RCs) associated with the gas, stars, and DM of each NIHAO disky galaxy. The galpy package was tested and used for that purpose. The DM inferred RCs are first obtained by subtracting the inferred gas and stellar components from the total mass profiles, as one would with real observations, and then compared with the true'' values directly inferred from the simulations. We find excellent agreement between the inferred and true'' mass profiles for the DM at large galactocentric radii. However, in the central parts of galaxies, the mass offset can be significant, reaching differences as high as 50% for some systems, with an average of 10% offset measured at R = 0.02 R_200. The lack of bulge/disk decompositions or accounting for non-circular motions may account for the inferred discrepancies. These effects will be investigated in a future study.