Galactic star formation and supermassive black hole masses
Astronomers studying how star formation evolved over cosmic time have discovered that quiescent galaxies (galaxies that are currently not making many new stars) frequently have active galactic nuclei. These AGN accrete material onto hot circumnuclear disks, and the resultant energy is released in bursts of radiation, or as jets of particles moving at close to the speed of light. The suspicion is that these outbursts drive gas outflows over thousands of light-years, disrupting and dispersing potential star forming material in a process called quenching. The quenching mechanism is in addition a self-limiting one since the dispersion ultimately suppresses the gas accretion onto the black hole itself. There are other proposed mechanisms for quenching however: supernovae produced during star formation could be responsible (or at least an important contributor) as could strong stellar winds. Verifying these various alternatives is hence a key goal of galactic research.