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Massive, red galaxies in a hierarchical universe – I. Counts of extremely red objects and basic properties.

Gonzalez-Perez, V. and Baugh, C.M. and Lacey, C.G. and Almeida, C. (2009) 'Massive, red galaxies in a hierarchical universe – I. Counts of extremely red objects and basic properties.', Monthly notices of the Royal Astronomical Society., 398 (2). pp. 497-514.


We present predictions for the abundance and nature of extremely red objects (EROs) in the Λ cold dark matter model. EROs are red, massive galaxies observed at z≥ 1 and their numbers and properties pose a challenge to hierarchical galaxy formation models. We compare the predictions from two published models, one of which invokes a ‘superwind’ to regulate star formation in massive haloes and the other which suppresses gas cooling in haloes through ‘radio-mode’ active galactic nucleus (AGN) feedback. The superwind model underestimates the number counts of EROs by an order of magnitude, whereas the radio-mode AGN feedback model gives excellent agreement with the number counts and redshift distribution of EROs. In the AGN feedback model the ERO population is dominated by old, passively evolving galaxies, whereas observations favour an equal split between old galaxies and dusty starbursts. Also, the model predicts a more extended redshift distribution of passive galaxies than is observed. These comparisons suggest that star formation may be quenched too efficiently in this model.

Item Type:Article
Keywords:Galaxies: evolution, Galaxies: formation, Galaxies: high-redshift, Cosmology: theory.
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Publisher statement:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2009 The Authors. Published by Oxford University Press on behalf of The Royal Astronomical Society. All rights reserved.
Date accepted:No date available
Date deposited:29 January 2015
Date of first online publication:September 2009
Date first made open access:No date available

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