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Ghostly Galaxies: Accretion-dominated Stellar Systems in Low-mass Dark Matter Halos

Wang, Chung-Wen; Cooper, Andrew P.; Bose, Sownak; Frenk, Carlos S.; Hellwing, Wojciech A.

Ghostly Galaxies: Accretion-dominated Stellar Systems in Low-mass Dark Matter Halos Thumbnail


Chung-Wen Wang

Andrew P. Cooper

Sownak Bose

Wojciech A. Hellwing


Wide-area deep imaging surveys have discovered large numbers of extremely low surface brightness (LSB) dwarf galaxies, which challenge galaxy formation theory and, potentially, offer new constraints on the nature of dark matter. Here we discuss one as-yet-unexplored formation mechanism that may account for a fraction of LSB dwarfs. We call this the "ghost galaxy" scenario. In this scenario, inefficient radiative cooling prevents star formation in the "main branch" of the merger tree of a low-mass dark matter halo, such that almost all its stellar mass is acquired through mergers with less massive (but nevertheless star-forming) progenitors. Present-day systems formed in this way would be "ghostly" isolated stellar halos with no central galaxy. We use merger trees based on the extended Press–Schechter formalism and the Copernicus Complexio cosmological N-body simulation to demonstrate that mass assembly histories of this kind can occur for low-mass halos in ΛCDM, but they are rare. They are most probable in isolated halos of present-day mass ∼4 × 109M⊙, occurring for ∼5% of all halos of that mass under standard assumptions about the timing and effect of cosmic reionization. The stellar masses of star-forming progenitors in these systems are highly uncertain; abundance-matching arguments imply a bimodal present-day mass function having a brighter population (median M⋆ ∼ 3 × 106 M⊙) consistent with the tail of the observed luminosity function of ultradiffuse galaxies. This suggests that observable analogs of these systems may await discovery. We find that a stronger ionizing background (globally or locally) produces brighter and more extended ghost galaxies.


Wang, C., Cooper, A. P., Bose, S., Frenk, C. S., & Hellwing, W. A. (2023). Ghostly Galaxies: Accretion-dominated Stellar Systems in Low-mass Dark Matter Halos. Astrophysical Journal, 958(2), Article 166.

Journal Article Type Article
Acceptance Date Oct 5, 2023
Online Publication Date Nov 22, 2023
Publication Date Dec 1, 2023
Deposit Date Feb 26, 2024
Publicly Available Date Feb 26, 2024
Journal The Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 958
Issue 2
Article Number 166
Keywords Space and Planetary Science; Astronomy and Astrophysics
Public URL


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