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The chosen few: the low-mass haloes that host faint galaxies

Sawala, Till; Frenk, Carlos S.; Fattahi, Azadeh; Navarro, Julio F.; Theuns, Tom; Bower, Richard G.; Crain, Robert A.; Furlong, Michelle; Jenkins, Adrian; Schaller, Matthieu; Schaye, Joop

The chosen few: the low-mass haloes that host faint galaxies Thumbnail


Till Sawala

Azadeh Fattahi

Julio F. Navarro

Richard G. Bower

Robert A. Crain

Michelle Furlong

Matthieu Schaller

Joop Schaye


Since reionization prevents star formation in most haloes less massive than 3 × 109 M⊙, dwarf galaxies only populate a fraction of existing dark matter haloes. We use hydrodynamic cosmological simulations of the Local Group to study the discriminating factors for galaxy formation in the early Universe and connect them to the present-day properties of galaxies and haloes. A combination of selection effects related to reionization, and the subsequent evolution of haloes in different environments, introduces strong biases between the population of haloes that host dwarf galaxies, and the total halo population. Haloes that host galaxies formed earlier and are more concentrated. In addition, haloes more affected by tidal stripping are more likely to host a galaxy for a given mass or maximum circular velocity, vmax, today. Consequently, satellite haloes are populated more frequently than field haloes, and satellite haloes of 108–109 M⊙ or vmax of 12–20 km s−1, compatible with stellar kinematics of Local Group dwarf spheroidals, have experienced a greater than average reduction in both mass and vmax after infall. They are on closer, more radial orbits with higher infall velocities and earlier infall times. Together, these effects make dwarf galaxies highly biased tracers of the underlying dark matter distribution.


Sawala, T., Frenk, C. S., Fattahi, A., Navarro, J. F., Theuns, T., Bower, R. G., …Schaye, J. (2016). The chosen few: the low-mass haloes that host faint galaxies. Monthly Notices of the Royal Astronomical Society, 456(1), 85-97.

Journal Article Type Article
Acceptance Date Nov 3, 2015
Online Publication Date Dec 11, 2015
Publication Date Feb 11, 2016
Deposit Date Feb 19, 2016
Publicly Available Date Feb 23, 2016
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 456
Issue 1
Pages 85-97
Keywords Methods: numerical, Galaxies: dwarf, Galaxies: formation, Local Group, Cosmology: theory.


Published Journal Article (2.1 Mb)

Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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