12:00 pm Zoom Room (online)
Philip Mansfield, "Why Do Dark Matter Halos Die Together? An Intergalactic Murder Mystery"
PhD Advisor: Andrey V. Kravtsov
Galaxies live their lives deep within massive invisible clumps of dark matter called "dark matter halos." The overwhelming gravity of dark matter halos cause their growth and evolution to control and dominate the long-term growth of the galaxies within them. This fact has been widely used to compare our largest galaxy surveys against the predictions of our cosmological models. However, this endeavor faces a long-standing theoretical problem: "dying" dark matter halos (halos whose growth has slowed to a trickle over the past few billion years) are preferentially found nearby one another. This means that large-scale environment is strongly connected to the growth and properties of dark matter halos, and likely their galaxies, too. This connection between halo growth and environment is called "assembly bias." Attempts to mitigate the impact of assembly bias on galaxy models have been stymied by the fact that even after 15 years of study it is still unclear why assembly bias occurs. In this thesis defense, I argue for a model which unifies the disparate theoretical camps into a single explanation for galaxy-mass assembly bias. This defense will also touch on my teaching work while at the University of Chicago.