Description:

Abstract: Great observational progress over the past decade has revealed how galaxies have changed over cosmic time.  One surprising revelation was the existence of massive, “red and dead” galaxies which had already reached masses exceeding that of the Milky Way and ceased forming stars (or “quenched”) only a few gigayears after the Big Bang.  These objects present a challenge to theorists: how can they form and quench so quickly?  I will discuss some recent simulation studies of these objects, and use them as a focus to examine one of the major outstanding questions in galaxy formation theory: how do supermassive black holes (SMBHs) coevolve with their host galaxies, and [how] are they responsible for galaxy quenching?  I will begin with an overview of the known observational scaling relations, the physics of galaxy formation, and how that physics is implemented in simulations, and show a few examples of how we can learn about the formation of massive galaxies using different simulation approaches.  A major uncertain element in simulating galaxy formation is the implementation of SMBH physics, since it occurs at scales well below the achievable spatial resolution.  Because the fundamental physics is unresolved, simulators have significant flexibility in choosing how to implement it at the galaxy scale. In the latter portion of my talk, I will present results from a large suite of zoom-in simulations exploring a variety of implementations and parameterizations for modeling SMBH physics to address the question: what are the common physical properties of SMBH models that produce realistic quenching behavior at different halo mass scales?

Speaker: Sarah Wellons, NSF Astronomy & Astrophysics Fellow, Northwestern University