The Physics of Satellite Galaxy Quenching: Novel Analysis of Observations, and High-Resolution Simulations

University Of California-Irvine, Irvine CA

Investigators

Abstract

This project will study the physical mechanisms responsible for halting the formation of stars in satellite galaxies. These galaxies, which orbit more massive galaxies, represent a large segment of the global galaxy population. They are poorly understood. The proposed research will combine analysis of imaging and spectroscopic datasets as well as computer simulations to study the physical mechanism for quenching of star formation in these satellite galaxies. Dr. Cooper will also educate and mentor underrepresented students as part of the new Cal-Bridge program, which is designed to increase the number of minority students who successfully transition from Cal State Universities into graduate school at UC campuses in astrophysics or physics. As a core member of the program, Dr. Cooper will serve as a one-on-one mentor and research advisor to individual Cal-Bridge scholars, while also developing day-long, program-wide professional development seminars, focusing on topics ranging from scientific coding to preparation for the GRE exam. Despite success at modeling the evolution of massive galaxies over cosmic time, modern models of galaxy formation fail to reproduce the properties of low-mass galaxies over cosmic time. This shortcoming in our theoretical picture is largely driven by an inability to understand the physics of satellite (or "environmental") quenching. To address this shortcoming, the proposed research program employs observations of satellite galaxies across a broad range in stellar mass and host halo mass at z < 2 in tandem with a focused semi-analytic modeling effort, to identify the particular physical mechanisms at play once a satellite is accreted onto a host halo. The proposed analysis will test a model whereby starvation and ram-pressure stripping are the dominant quenching mechanisms above and below a critical scale, respectively. Dr. Cooper will lead a targeted spectroscopic campaign to catalog an unprecedented sample of satellite galaxies in groups at z ~ 1. This effort will be complemented by a statistical analysis of satellites at z < 2 using deep imaging in legacy extragalactic fields. This program will significantly expand our knowledge of the physical processes that quench satellites and drive the build-up of the quiescent galaxy population at z < 2, directly addressing a major failure of current galaxy formation models. In addition, Dr. Cooper will educate and mentor underrepresented students as part of the new Cal-Bridge program, which is designed to increase the number of minority students who successfully transition from Cal State Universities into graduate school at UC campuses in astrophysics or physics. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.