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The baryon fraction of Lambda CDM haloes

Crain, RA and Eke, VR and Frenk, CS and Jenkins, A and McCarthy, IG and Navarro, JF and Pearce, FR (2007) The baryon fraction of Lambda CDM haloes. Monthly Notices of the Royal Astronomical Society, 377 (1). pp. 41-49. ISSN 0035-8711

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Abstract

We investigate the baryon fraction in dark matter haloes formed in non-radiative gasdynamical simulations of the �CDM cosmogony. By combining a realisation of the Millennium
Simulation (Springel et al.) with a simulation of a smaller volume focussing on dwarf haloes, our study spans five decades in halo mass, from 1010 h−1 M⊙ to 1015 h−1 M⊙. We
find that the baryon fraction within the halo virial radius is typically 90% of the cosmic mean, with an rms scatter of 6%, independently of redshift and of halo mass down to the smallest resolved haloes. Our results show that, contrary to the proposal of Mo et al. (2005), previrialisation
gravitational heating is unable to prevent the collapse of gas within galactic and proto-galactic haloes, and confirm the need for non-gravitational feedback in order to reduce
the efficiency of gas cooling and star formation in dwarf galaxy haloes. Simulations including a simple photo-heatingmodel (where a gas temperature floor of Tfloor = 2×104 K is imposed from z = 11) confirm earlier suggestions that photoheating can only prevent the collapse of
baryons in systems with virial temperatures T200 . 2.2 Tfloor � 4.4 × 104 K (corresponding to a virial mass of M200 � 1010 h−1 M⊙ and a circular velocity of V200 � 35 km s−1). Photoheating may thus help regulate the formation of dwarf spheroidals and other galaxies at the extreme faint-end of the luminosity function, but it cannot, on its own, reconcile the abundance of sub-L⋆ galaxies with the vast number of dwarf haloes expected in the �CDM cosmogony. The lack of evolution or mass dependence seen in the baryon fraction augurs well for X-ray cluster studies that assume a universal and non-evolving baryon fraction to place constraints on cosmological parameters.

Item Type: Article
Additional Information: This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record MNRAS (2007) 337(1) 41-49 is available online at:http://dx.doi.org/10.1111/j.1365-2966.2007.11598.x
Uncontrolled Keywords: 0201 Astronomical And Space Sciences
Subjects: Q Science > QB Astronomy
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press
Related URLs:
Date Deposited: 12 Feb 2015 13:55
Last Modified: 17 Apr 2015 13:36
DOI or Identification number: 10.1111/j.1365-2966.2007.11598.x
URI: http://researchonline.ljmu.ac.uk/id/eprint/455

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