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Events on Thursday, October 12th, 2023

Astronomy Colloquium
Searching for the Impact of Active Galactic Nuclei in Galaxy Quenching
Time: 3:30 pm - 4:30 pm
Place: 4421 Sterling Hall
Speaker: Prof. Decker French, The University of Illinois at Urban-Champaign
Abstract: AGN feedback is expected to have a key role in the evolution of galaxies, especially as galaxies evolve from star-forming to quiescent. However, direct connections between observations of AGN activity and the quenching of galaxies have been difficult. AGN vary on all timescales, with complete duty cycles more rapid than the timescales to observe evolutionary trends in galaxies. Wide-field spectroscopic observations provide a key observational constraint on the past AGN histories of galaxies through the detection of extended emission line regions. The effects of past AGN activity can be observed if gas surrounding the galaxy is illuminated by a nuclear source, even if the AGN has faded. Extreme examples of this can be observed as "voorwerps" in broadband imaging, but spectroscopy is needed to find and characterize fainter cases. I will present recent work using MaNGA observations of galaxies in the process of quenching after a starburst (post-starburst galaxies). Using MaNGA observations of multiple post-starburst galaxy samples, we see extended emission line regions due to past AGN activity. These observations allow us to constrain the duty cycle of AGN activity during this transitionary phase of galaxy evolution over a long time baseline of 10^4 - 10^5 years. This intermittent AGN activity may play a role in suppressing star formation, driving low velocity outflows, and removing molecular gas in quenching galaxies.
Host: Ke Zhang
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