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The evolution of the star-forming sequence in hierarchical galaxy formation models.

Mitchell, P.D. and Lacey, C.G. and Cole, S. and Baugh, C.M. (2014) 'The evolution of the star-forming sequence in hierarchical galaxy formation models.', Monthly notices of the Royal Astronomical Society., 444 (3). pp. 2637-2664.


It has been argued that the specific star formation rates of star-forming galaxies inferred from observational data decline more rapidly below z = 2 than is predicted by hierarchical galaxy formation models. We present a detailed analysis of this problem by comparing predictions from the galform semi-analytic model with an extensive compilation of data on the average star formation rates of star-forming galaxies. We also use this data to infer the form of the stellar mass assembly histories of star-forming galaxies. Our analysis reveals that the currently available data favour a scenario where the stellar mass assembly histories of star-forming galaxies rise at early times and then fall towards the present day. In contrast, our model predicts stellar mass assembly histories that are almost flat below z = 2 for star-forming galaxies, such that the predicted star formation rates can be offset with respect to the observational data by factors of up to 2–3. This disagreement can be explained by the level of coevolution between stellar and halo mass assembly that exists in contemporary galaxy formation models. In turn, this arises because the standard implementations of star formation and supernova feedback used in the models result in the efficiencies of these process remaining approximately constant over the lifetime of a given star-forming galaxy. We demonstrate how a modification to the time-scale for gas ejected by feedback to be reincorporated into galaxy haloes can help to reconcile the model predictions with the data.

Item Type:Article
Keywords:Galaxies: evolution, Galaxies: formation, Galaxies: star formation.
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Publisher statement:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:09 August 2014
Date deposited:18 September 2014
Date of first online publication:11 September 2014
Date first made open access:No date available

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