Tiny galaxies and dark substructures: exploring the "dark" subhaloes in TNG50

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Main Authors: Doppel, Jessica E., Jauzac, Mathilde, Lagattuta, David J., Fattahi, Azadeh, Mahler, Guillaume
Format: Preprint
Published: 2025
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author Doppel, Jessica E.
Jauzac, Mathilde
Lagattuta, David J.
Fattahi, Azadeh
Mahler, Guillaume
author_facet Doppel, Jessica E.
Jauzac, Mathilde
Lagattuta, David J.
Fattahi, Azadeh
Mahler, Guillaume
contents Dark matter haloes and subhaloes that host no luminous counterpart are predicted within our current understanding of galaxy formation within a $Λ$CDM paradigm. Observational tests, such as gravitational lensing, have made potential detections of such objects around individual galaxies as well as in galaxy groups and clusters. The question of whether or not a dim counterpart might reside in these objects remains an open question. We investigate this point using the TNG50-1 simulation of the IllustrisTNG project. Under the assumption of TNG50's galaxy formation model, we do not find haloes or subhaloes above a total mass of $\rm 10^{9.7} \ M_{\odot}$ that are entirely dark. However, under realistic effective surface brightness cuts of $\rm \leq 29 \ mag \ arcsec^{-2}$, the inference of the most massive dark subhalo in galaxy groups and clusters becomes $\rm M_{DM} \gtrsim 2 \times 10^{10} \ M_{\odot}$. Concentrating on galaxy groups and clusters, we find that dark subhaloes are ubiquitous with more massive dark subhaloes tending to preferentially reside further from the centers of clusters. We find that subhaloes in the mass range of $\rm 4.5 \times 10^{7} \leq M_{DM}/M_{\odot} \leq 2.1\times 10^{8}$ tend to be the most likely to reside in the strong lensing regions of galaxy groups and clusters, and argue that future dark subhalo searches should investigate this mass range.
format Preprint
id arxiv_https___arxiv_org_abs_2506_09122
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Tiny galaxies and dark substructures: exploring the "dark" subhaloes in TNG50
Doppel, Jessica E.
Jauzac, Mathilde
Lagattuta, David J.
Fattahi, Azadeh
Mahler, Guillaume
Astrophysics of Galaxies
Cosmology and Nongalactic Astrophysics
Dark matter haloes and subhaloes that host no luminous counterpart are predicted within our current understanding of galaxy formation within a $Λ$CDM paradigm. Observational tests, such as gravitational lensing, have made potential detections of such objects around individual galaxies as well as in galaxy groups and clusters. The question of whether or not a dim counterpart might reside in these objects remains an open question. We investigate this point using the TNG50-1 simulation of the IllustrisTNG project. Under the assumption of TNG50's galaxy formation model, we do not find haloes or subhaloes above a total mass of $\rm 10^{9.7} \ M_{\odot}$ that are entirely dark. However, under realistic effective surface brightness cuts of $\rm \leq 29 \ mag \ arcsec^{-2}$, the inference of the most massive dark subhalo in galaxy groups and clusters becomes $\rm M_{DM} \gtrsim 2 \times 10^{10} \ M_{\odot}$. Concentrating on galaxy groups and clusters, we find that dark subhaloes are ubiquitous with more massive dark subhaloes tending to preferentially reside further from the centers of clusters. We find that subhaloes in the mass range of $\rm 4.5 \times 10^{7} \leq M_{DM}/M_{\odot} \leq 2.1\times 10^{8}$ tend to be the most likely to reside in the strong lensing regions of galaxy groups and clusters, and argue that future dark subhalo searches should investigate this mass range.
title Tiny galaxies and dark substructures: exploring the "dark" subhaloes in TNG50
topic Astrophysics of Galaxies
Cosmology and Nongalactic Astrophysics
url https://arxiv.org/abs/2506.09122