Galaxy Formation Insights from Constraints on the Galaxy-Halo Connection
Abstract
In this thesis I explore the relationship between galaxies and dark matter halos. Understanding this relationship allows us to quantify how correlated are galaxy formation and dark halo formation, and thus how much control the dark sector exerts over the nature and properties of the galaxy distribution that we see today. In the first part of this thesis, I develop new methods to measure the scatter in galaxy mass at fixed dark matter halo mass. Because we cannot measure halo mass directly, this quantity must be inferred indirectly. Previous measurements have focused entirely on massive galaxies in massive halos, ignoring Milky Way mass galaxies, which is the galaxy scale at which most stars are formed. I will show that the scatter at this mass is much larger than previous measurements have found for this mass scale, comparing favorably with the predictions of simulations and other models.
In the second part of my thesis I use the total amount of light within the satellites of a dark halo as a proxy for the dark halo growth rate. This observable, Lsat, has been measured for all central galaxies in the Sloan Digital Sky Legacy Survey. I compare these measurements to predictions from the Illustris TNG hydrodynamic simulation. I explore the trend in Lsat as a function of galaxy star formation rate at fixed galaxy mass. I find that the TNG predictions agree with the SDSS measurements for blue galaxies, but are inconsistent with the measurements for red galaxies. This implies that the strength of the correlation between galaxy star formation rate and dark halo growth rate within the TNG is comparable to that in the real universe, but only for blue galaxies. The mechanism that shuts off star formation in the TNG is not compatible with the mechanism that populates the red sequence in the real universe.- Publication:
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Ph.D. Thesis
- Pub Date:
- 2021
- Bibcode:
- 2021PhDT........13C
- Keywords:
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- Physics; Astronomy; Astrophysics; Simulation; Velocity; Star & galaxy formation; Dark matter; Stars & galaxies; Methods; Satellites; Universe