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Special Presentations

Examining the Mass Functions of Galaxies with the RESOLVE Survey

Presented by: Kathleen Eckert (University of Pennsylvania – Dept of Physics & Astronomy)
Category: Special Interest   Duration: 1 hour   Broadcast date: February 19, 2019
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There are several outstanding problems facing our understanding of galaxy formation and evolution, including the apparent shortfall of observed dwarf galaxies compared to theoretical expectations. The galaxy mass function is often used to characterize the galaxy population for comparison with the halo mass function from simulations of dark matter. Although galaxy mass is typically defined by the stellar mass, for low-mass galaxies, the cold atomic gas can be the dominant observable mass component. Since cold gas measurements are time-intensive relative to photometry, I will present a new photometric gas mass estimator that yields unbiased gas mass estimates for volume-limited galaxy surveys. Using this new estimator, I will compare the stellar and cold-baryonic (stars + cold atomic gas) mass functions of galaxies and galaxy groups in the RESOLVE and ECO surveys, two volume-limited galaxy surveys that are complete for galaxies with cold baryonic mass > 10^9 Msun. I find that the galaxy cold-baryonic mass function rises with a steeper low-mass slope than the stellar mass function. Additionally, I will show that the mass function divided into different group halo mass regimes reveals interesting structure, in particular - a flat low mass slope for groups of intermediate mass (~10^12 Msun) that may be related to environmental processes such as merging and stripping. Finally, I will also provide a short overview of weak lensing shear estimation with the Bayesian Fourier Domain method, showing that we can produce an unbiased estimate of shear without the need for calibration simulations.