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The abundance of (not just) dark matter haloes.

Sawala, T. and Frenk, C.S. and Crain, R.A. and Jenkins, A. R. and Schaye, J. and Theuns, Tom and Zavala, J. (2013) 'The abundance of (not just) dark matter haloes.', Monthly notices of the Royal Astronomical Society., 431 (2). pp. 1366-1382.


We study the effect of baryons on the abundance of structures and substructures in a Λ cold dark matter (CDM) cosmology, using a pair of high-resolution cosmological simulations from the Galaxies-Intergalactic Medium Interaction Calculation project. Both simulations use identical initial conditions, but while one contains only dark matter, the other also includes baryons. We find that gas pressure, reionization, supernova feedback, stripping and truncated accretion systematically reduce the total mass and the abundance of structures below ∼1012 M⊙ compared to the pure dark matter simulation. Taking this into account and adopting an appropriate detection threshold lower the abundance of observed galaxies with maximum circular velocities vmax < 100 km s−1, significantly reducing the reported discrepancy between ΛCDM and the measured H I velocity function of the Arecibo Legacy Fast ALFA survey. We also show that the stellar-to-total mass ratios of galaxies with stellar masses of ∼105–107 M⊙ inferred from abundance matching of the (sub)halo mass function to the observed galaxy mass function increase by a factor of ∼2. In addition, we find that an important fraction of low-mass subhaloes are completely devoid of stars. Accounting for the presence of dark subhaloes below 1010 M⊙ further reduces the abundance of observable objects and leads to an additional increase in the inferred stellar-to-total mass ratio by factors of 2–10 for galaxies in haloes of 109–1010 M⊙. This largely reconciles the abundance matching results with the kinematics of individual dwarf galaxies in ΛCDM. We propose approximate corrections to the masses of objects derived from pure dark matter calculations to account for baryonic effects.

Item Type:Article
Keywords:Galaxies: evolution, Galaxies: formation, Galaxies: luminosity function, Mass function, Cosmology: theory.
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Publisher statement:This article has been accepted for publication in Monthly notices of the Royal Astronomical Society © 2013 The Authors Published by Oxford University Press on behalf of Royal Astronomical Society. All rights reserved.
Date accepted:No date available
Date deposited:27 June 2014
Date of first online publication:May 2013
Date first made open access:No date available

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