Institute of Astronomy

How is star formation in galaxies quenched?

SpeakerTalk DateTalk Series
Asa Bluck (Cavendish)29 November 2019Institute of Astronomy Galaxies Discussion Group


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.


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