Enhanced density fluctuations: consequences for stellar dynamics and dark matter substructure
Abstract
Enhanced density fluctuations form early dark matter halos, which serve as early gravitational potential wells for baryons. These baryons can then condense to form stars and black holes at high redshifts, 1+z ≳ 100. Larger density fluctuations result in denser halos with higher virial temperatures; hence, a halo at a mass that is below the threshold for forming stars under standard astrophysical expectations may form astrophysical objects if its initial density is higher than expected, although the exact threshold for compact object formation is subject to large astrophysical uncertainties. We outline the conditions under which enhanced density fluctuations form dark (star-less) halos, early galaxies, or even star clusters. Using toy model enhancements to the primordial power spectrum that have been shown to explain the abundances of ``little red dots", along with our fiducial set of astrophysical parameters, we show that the number of clusters initially captured by the Milky Way is highly sensitive to the shape of the enhancement, with the narrowly peaked enhancement resulting in $50$ clusters and the step-function enhancement resulting in ∼ 4.1 × 105. The initial stellar masses of the clusters is also O (100) M⊙, although this range is also dependent on the shape of the enhancement. In addition, the abundance of dark matter subhalos with masses greater than 107 M⊙ can be enhanced by as much as a factor of ∼ 6.5 and is denser than in ΛCDM, which will increase their detectability in future stellar stream surveys such as the Via Project.
Related
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- Limits on the size of electron density fluctuations in the early universe and implications for the Hubble tension
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BibTeX
@misc{qin2026enhanced,
title = {{Enhanced density fluctuations: consequences for stellar dynamics and dark matter substructure}},
author = {Wenzer Qin and David E. Kaplan and Neal Weiner},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.35991},
eprint = {2609.35991},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.35991},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Enhanced density fluctuations: consequences for stellar dynamics and dark matter substructure
AU - Wenzer Qin
AU - David E. Kaplan
AU - Neal Weiner
PY - 2026
DA - 2026/09/28
PB - arXiv
DO - 10.48550/arxiv.2609.35991
UR - https://arxiv.org/abs/2609.35991
AB - Enhanced density fluctuations form early dark matter halos, which serve as early gravitational potential wells for baryons. These baryons can then condense to form stars and black holes at high redshifts, 1+z ≳ 100. Larger density fluctuations result in denser halos with higher virial temperatures; hence, a halo at a mass that is below the threshold for forming stars under standard astrophysical expectations may form astrophysical objects if its initial density is higher than expected, although the exact threshold for compact object formation is subject to large astrophysical uncertainties. We outline the conditions under which enhanced density fluctuations form dark (star-less) halos, early galaxies, or even star clusters. Using toy model enhancements to the primordial power spectrum that have been shown to explain the abundances of ``little red dots", along with our fiducial set of astrophysical parameters, we show that the number of clusters initially captured by the Milky Way is highly sensitive to the shape of the enhancement, with the narrowly peaked enhancement resulting in $50$ clusters and the step-function enhancement resulting in ∼ 4.1 × 10^5. The initial stellar masses of the clusters is also O (100) M_⊙, although this range is also dependent on the shape of the enhancement. In addition, the abundance of dark matter subhalos with masses greater than 10^7 M_⊙ can be enhanced by as much as a factor of ∼ 6.5 and is denser than in ΛCDM, which will increase their detectability in future stellar stream surveys such as the Via Project.
ER -