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Luminous red galaxies in hierarchical cosmologies.

Almeida, C. and Baugh, C.M. and Wake, D.A. and Lacey, C.G. and Benson, A.J. and Bower, R.G. and Pimbblet, K. (2008) 'Luminous red galaxies in hierarchical cosmologies.', Monthly notices of the Royal Astronomical Society., 386 (4). pp. 2145-2160.


Luminous red galaxies (LRGs) are much rarer and more massive than L* galaxies. Coupled with their extreme colours, LRGs therefore provide a demanding testing ground for the physics of massive galaxy formation. We present the first self-consistent predictions for the abundance and properties of LRGs in hierarchical structure formation models. We test two published models which use quite different mechanisms to suppress the formation of massive galaxies: the Bower et al. model which invokes ‘active galactic nuclei (AGN) feedback’ to prevent gas from cooling in massive haloes and the Baugh et al. model which relies upon a ‘superwind’ to eject gas before it is turned into stars. Without adjusting any parameters, the Bower et al. model gives an excellent match to the observed luminosity function of LRGs in the Sloan Digital Sky Survey (with a median redshift of z= 0.24) and to their clustering; the Baugh et al. model is less successful in these respects. Both models fail to match the observed abundance of LRGs at z= 0.5 to better than a factor of ≈2. In the models, LRGs are typically bulge-dominated systems with stellar masses of ≈2 × 1011h−1M⊙ and velocity dispersions of σ∼ 250 km s−1. Around half of the stellar mass in the model LRGs is already formed by z∼ 2.2 and is assembled into one main progenitor by z∼ 1.5; on average, only 25 per cent of the mass of the main progenitor is added after z∼ 1. LRGs are predicted to be found in a wide range of halo masses, a conclusion which relies on properly taking into account the scatter in the formation histories of haloes. Remarkably, we find that the correlation function of LRGs is predicted to be a power law down to small pair separations, in excellent agreement with observational estimates. Neither the Bower et al. nor the Baugh et al. model is able to reproduce the observed radii of LRGs.

Item Type:Article
Keywords:Galaxies: elliptical and lenticular, cD, Galaxies: evolution, Cosmology: theory, Large-scale structure of Universe.
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Publisher statement:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2008 The Authors. Published by Oxford University Press on behalf of The Royal Astronomical Society. All rights reserved.
Record Created:28 Jan 2015 14:35
Last Modified:16 Feb 2015 11:24

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