Supermassive Black Holes and the End of Star Formation
The Standard Model of Cosmology (Lambda-CDM, i.e. the cosmological constant, Lambda, together with cold dark matter, CDM) fits many observations well. But there is a fair number of observations that don't match its predictions. These discrepancies might indicate that we don't understand the astrophysics of the associated phenomena well enough to make appropriate predictions. Alternatively, each false prediction also points to a potential weakness in the overall model. In particular, a large number of recent observations of the early Universe have been difficult to interpret using the models and astrophysical understanding that we developed by studying the older, closer Universe.
Tonight's speaker is Dr Chelsea Sharon. Dr Sharon has been exploring one of these discrepancies associated with the influences that supermassive black holes have on their host galaxies. She'll help us understand the problem and share what she's learned about it so far. Her description of her presentation is below.
With modern instrumentation and observations we have entered the era of precision cosmology, where the relative amounts of baryonic matter, dark matter and dark energy are well constrained. Based on the resulting cosmological model, we can predict the number of galaxies that should exist as a function of their mass. However, observed galaxy populations do not match this predicted distribution, particularly for the most massive systems. Theoretical work suggests that active galactic nuclei (AGN), supermassive black holes at the centers of galaxies that are consuming the surrounding gas, may suppress star formation. However, the exact method for quenching star formation is poorly understood, and direct evidence for AGN affecting the molecular clouds that fuel star formation is sparse. I will discuss how new and ongoing observations from the Karl G. Jansky Very Large Array and Atacama Large Millimeter Array can be used to determine whether AGN prevented the overproduction of massive galaxies in the early universe, when star formation and AGN activity peaked.
About Dr Chelsea Sharon
Dr. Chelsea Sharon grew up in the small town of Grass Valley, California, where her love of astronomy was sparked by coffee-table books filled with Hubble images and the profound questions they explore about our Universe. She got her BS in astrophysics from the California Institute of Technology and PhD from Rutgers, the State University of New Jersey, where she specialized in radio spectroscopy of galaxies in the early Universe and first developed her passion for teaching. After postdoctoral research appointments at Cornell University and McMaster University, she became faculty at (the unfortunately short-lived) Yale-NUS College in Singapore. Following its closure, Chelsea happily found her way to the beautiful Pacific Northwest, where she now focusses on teaching astronomy and scientific reasoning at Clackamas Community College. Her research addresses how galaxies evolve across cosmic time, with a particular focus on star formation, molecular clouds, and supermassive black holes.