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Satellite mass functions and the faint end of the galaxy mass–halo mass relation in LCDM

Santos-Santos, Isabel ME; Sales, Laura V; Fattahi, Azadeh; Navarro, Julio F

Satellite mass functions and the faint end of the galaxy mass–halo mass relation in LCDM Thumbnail


Laura V Sales

Azadeh Fattahi

Julio F Navarro


The abundance of the faintest galaxies provides insight into the nature of dark matter and the process of dwarf galaxy formation. In the LCDM scenario, low-mass haloes are so numerous that the efficiency of dwarf formation must decline sharply with decreasing halo mass in order to accommodate the relative scarcity of observed dwarfs and satellites in the Local Group. The nature of this decline contains important clues to the mechanisms regulating the onset of galaxy formation in the faintest systems. We explore here two possible models for the stellar mass (M*)–halo mass (M200) relation at the faint end, motivated by some of the latest LCDM cosmological hydrodynamical simulations. One model includes a sharp mass threshold below which no luminous galaxies form, as expected if galaxy formation proceeds only in systems above the hydrogen-cooling limit. In the second model, M* scales as a steep power law of M200 with no explicit cut-off, as suggested by recent semi-analytical work. Although both models predict satellite numbers around Milky Way-like galaxies consistent with current observations, they predict vastly different numbers of ultrafaint dwarfs and of satellites around isolated dwarf galaxies. Our results illustrate how the satellite mass function around dwarfs may be used to probe the M*–M200 relation at the faint end and to elucidate the mechanisms that determine which low-mass haloes ‘light up’ or remain dark in the LCDM scenario.


Santos-Santos, I. M., Sales, L. V., Fattahi, A., & Navarro, J. F. (2022). Satellite mass functions and the faint end of the galaxy mass–halo mass relation in LCDM. Monthly Notices of the Royal Astronomical Society, 515(3), 3685-3697.

Journal Article Type Article
Acceptance Date Jul 18, 2022
Online Publication Date Jul 23, 2022
Publication Date 2022-09
Deposit Date Sep 15, 2022
Publicly Available Date Sep 15, 2022
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 515
Issue 3
Pages 3685-3697
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Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. ©: 2022 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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