Institute of Astronomy

Why do galaxies stop forming stars?

SpeakerTalk DateTalk Series
Asa Bluck6 March 2019Institute of Astronomy Seminars

Abstract

I will present an overview of my ongoing research into galactic star
formation and its cessation in the ‘quenching’ process. From an analysis
of the SDSS, we discover that the fraction of quenched central galaxies
scales most tightly with estimates of supermassive black hole mass. This
result is consistent with models which quench centrals through AGN
feedback, particularly in the so called ‘radio-mode’. However, satellite
galaxies require additional quenching mechanisms, strongly correlated
with environment. I will also present new work examining resolved star
formation and quenching in galaxies using the MaNGA survey. Through a
detailed machine learning analysis, we conclude that global properties
(particularly those most connected with the central regions in galaxies)
are the most predictive of quenching in both centrals and satellites.
Perhaps surprisingly, the conditions at the spaxel location are largely
uncorrelated with quenching. Conversely, we find that local parameters
are most effective at predicting the rate of star formation in star
forming regions. From these results, we conclude that quenching is a
globally governed process (affecting entire galaxies as a whole), but
star formation is a locally governed process (varying significantly
throughout galaxies, depending on local conditions).

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