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How is star formation in galaxies quenched?

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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 (derived via scaling relations with central kinematics). I will show that this result is highly consistent with models which quench centrals through AGN -feedback, particularly in the ‘radio-mode’. However, satellite galaxies require additional quenching mechanisms, strongly correlated with environment (including local density and location within the group or cluster).

I will also present new work examining resolved star formation and quenching in galaxies using the MaNGA IFU survey. We perform a detailed machine learning analysis of physical properties derived from over 5 million optical spectra, utilising artificial neural networks (ANN). We find that global properties (particularly those most connected with the central regions in galaxies) are the most predictive of quenching in centrals. Perhaps surprisingly, the conditions at the spaxel location are largely uncorrelated with quenching. Conversely, we find that local/ spatially resolved parameters are most effective at predicting the rate of star formation in star forming regions. From these results, we conclude that: 1) quenching is a global process, impacting entire galaxies as a whole; yet 2) star formation is a locally governed process, varying significantly throughout galaxies and depending primarily on local conditions. I will conclude by ruling out several quenching models on the basis of these results.

This talk is part of the Institute of Astronomy Galaxies Discussion Group series.

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