The Galaxy end sequence

Eales, Stephen ORCID: https://orcid.org/0000-0002-7394-426X, de Vis, Pieter, Smith, Matthew W. L. ORCID: https://orcid.org/0000-0002-3532-6970, Appah, Kiran, Ciesla, Laure, Duffield, Chris and Schofield, Simon 2017. The Galaxy end sequence. Monthly Notices of the Royal Astronomical Society 465 (3) , pp. 3125-3133. 10.1093/mnras/stw2875

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Abstract

A common assumption is that galaxies fall in two distinct regions of a plot of specific star formation rate (SSFR) versus galaxy stellar mass: a star-forming galaxy main sequence (GMS) and a separate region of ‘passive’ or ‘red and dead galaxies’. Starting from a volume-limited sample of nearby galaxies designed to contain most of the stellar mass in this volume, and thus representing the end-point of ≃12 billion years of galaxy evolution, we investigate the distribution of galaxies in this diagram today. We show that galaxies follow a strongly curved extended GMS with a steep negative slope at high galaxy stellar masses. There is a gradual change in the morphologies of the galaxies along this distribution, but there is no clear break between early-type and late-type galaxies. Examining the other evidence that there are two distinct populations, we argue that the ‘red sequence’ is the result of the colours of galaxies changing very little below a critical value of the SSFR, rather than implying a distinct population of galaxies. Herschel observations, which show at least half of early-type galaxies contain a cool interstellar medium, also imply continuity between early-type and late-type galaxies. This picture of a unitary population of galaxies requires more gradual evolutionary processes than the rapid quenching process needed to explain two distinct populations. We challenge theorists to predict quantitatively the properties of this ‘Galaxy End Sequence’.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Physics and Astronomy
Publisher:	Oxford University Press
ISSN:	0035-8711
Date of First Compliant Deposit:	25 April 2017
Date of Acceptance:	4 November 2016
Last Modified:	19 Nov 2024 05:15
URI:	https://orca.cardiff.ac.uk/id/eprint/100087

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