X-ray Insights into the Connection between Quenching of Star Formation and Galaxy Stellar Velocity Dispersion
Dr. Allison Man (firstname.lastname@example.org)
*All are welcome to this event!
There is a surprisingly tight correlation between galaxies with quenched star formation and their central velocity dispersion, which also correlated with the central black hole's mass. Those correlations suggest that the central black hole is the culprit. However, radio and X-ray observations of these galaxies show that the black hole's considerable energy production can bypass the galaxy and thermalize at distances tens of kiloparsecs from the galaxies' stars. The circumgalactic medium (CGM) may therefore be what connects black hole feedback with quenching of star formation. The CGM can be difficult to observe, but X-ray observations have yielded important clues about the how black holes and the CGM are connected.
We have proposed a "valve" model for that connection, whereby the black hole lifts the CGM, lowering the circumgalactic pressure and allowing two distinct states for the galaxy: a wind-dominated mode where winds from type 1a supernovae suppress gas cooling, and a precipitation-dominated mode where cool gas can rain from the hot CGM. This cold "multi-phase" gas can feed the black hole and trace amounts of star formation, completing and sustaining the feedback cycle that keeps a galaxy quenching. The central velocity dispersion - the observational signature of the central gravitational potential - may determine which state prevails in each galaxy.
We will discuss what the X-ray observations have shown so far, and what future X-ray and UV observations may unlock.
Megan Donahue studies clusters of galaxies. Cluster evolution tells us about the matter density of the universe, because the formation of galaxy clusters is governed by gravitational physics. She pays particular attention to how clusters are found, because any bias in finding clusters can lead to a bias in our conclusions about them. She also studies the metallicity, distribution, and physics of intergalactic gas. Is this really where most of the baryons are hiding? Her work includes models and observational tests of cooling flows in the gas within clusters. Strange things are afoot in cluster cores and she would like to sort it out.
Professor Donahue was named a Fellow of the American Physical Society in October 2016 for "advanced cosmological observations and analyses of galaxy clusters, and of the relationship between the thermodynamic state of circumgalactic gas around massive galaxies, the triggering of active galactic nucleus feedback, and the regulation of star formation in galaxies" after nomination by the APS Division of Astrophysics.
Professor Donahue was elected as President of the American Astronomical Society (AAS) in 2017.
View Dr. Donahue's faculty webpage here
View her Home page here