Heavy black hole seed survivors in dwarf galaxies: a case study of Leo I

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Main Authors: Scoggins, Matthew T., Haiman, Zoltan, Pacucci, Fabio
Format: Preprint
Published: 2025
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author Scoggins, Matthew T.
Haiman, Zoltan
Pacucci, Fabio
author_facet Scoggins, Matthew T.
Haiman, Zoltan
Pacucci, Fabio
contents The supermassive black holes (SMBHs) with mass $M_\bullet > 10^9 \, \rm M_\odot$ hosted by high-redshift galaxies have challenged our understanding of black hole formation and growth, as several pathways have emerged attempting to explain their existence. The "heavy-seed" pathway eases the problem with the progenitors of these SMBHs having birth masses up to ${\sim} 10^5~{\rm M_\odot}$. Here, we investigate the possibility that a local dwarf galaxy, Leo I, harbors a heavy-seed descendant. Using Monte-Carlo merger trees to generate the merger histories of 1,000 dark matter halos similar to the Milky Way (MW; with a mass of ${\sim} 10^{12}~{\rm M_\odot}$ at redshift $z{=}0$). We search for Leo-like satellite halos among these merger trees, and investigate the probability that the progenitors of some of these satellites formed a heavy seed. We derive the likelihood of such "heavy seed survivors" (HSSs) across various formation and survival criteria as well as Leo-similarity criteria. We find that the virial temperature for the onset of atomic cooling and rapid gas infall that yields heavy seeds, $T_{\rm act}$, has the largest impact on the number of HSSs. We find HSSs in a fraction $0.7\%$, $18.1\%$, and $96.5\%$ of MW-like halos when $T_{\rm act}$ is set to $9,000$K, $7,000$K, and $5,000$K respectively. This suggests that Leo I could be hosting a heavy seed and could provide an opportunity to disentangle heavy seeds from other SMBH formation mechanisms.
format Preprint
id arxiv_https___arxiv_org_abs_2511_04736
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Heavy black hole seed survivors in dwarf galaxies: a case study of Leo I
Scoggins, Matthew T.
Haiman, Zoltan
Pacucci, Fabio
Astrophysics of Galaxies
High Energy Astrophysical Phenomena
The supermassive black holes (SMBHs) with mass $M_\bullet > 10^9 \, \rm M_\odot$ hosted by high-redshift galaxies have challenged our understanding of black hole formation and growth, as several pathways have emerged attempting to explain their existence. The "heavy-seed" pathway eases the problem with the progenitors of these SMBHs having birth masses up to ${\sim} 10^5~{\rm M_\odot}$. Here, we investigate the possibility that a local dwarf galaxy, Leo I, harbors a heavy-seed descendant. Using Monte-Carlo merger trees to generate the merger histories of 1,000 dark matter halos similar to the Milky Way (MW; with a mass of ${\sim} 10^{12}~{\rm M_\odot}$ at redshift $z{=}0$). We search for Leo-like satellite halos among these merger trees, and investigate the probability that the progenitors of some of these satellites formed a heavy seed. We derive the likelihood of such "heavy seed survivors" (HSSs) across various formation and survival criteria as well as Leo-similarity criteria. We find that the virial temperature for the onset of atomic cooling and rapid gas infall that yields heavy seeds, $T_{\rm act}$, has the largest impact on the number of HSSs. We find HSSs in a fraction $0.7\%$, $18.1\%$, and $96.5\%$ of MW-like halos when $T_{\rm act}$ is set to $9,000$K, $7,000$K, and $5,000$K respectively. This suggests that Leo I could be hosting a heavy seed and could provide an opportunity to disentangle heavy seeds from other SMBH formation mechanisms.
title Heavy black hole seed survivors in dwarf galaxies: a case study of Leo I
topic Astrophysics of Galaxies
High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2511.04736