article published yes Matthew T. Scoggins author Zoltán Haiman author 7c006e8c-cc0d-11ee-8322-cb904ef76f360000-0003-3633-5403 Fabio Pacucci author ZoHa department High-redshift supermassive black holes (SMBHs) have challenged our understanding of black hole formation and growth. The ‘heavy-seed’ pathway eases the problem with the progenitors of these SMBHs having birth masses up to∼105 M. Here, we investigate the possibility that a local dwarf galaxy, Leo I, harbours a heavy-seed descendant. Using Monte Carlo merger trees to generate the merger histories of 1000 dark matter haloes similar to the Milky Way (MW), we search for Leo- like satellite haloes and investigate the probability that the progenitors 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, Tact , has the largest impact on HSS frequency. We find HSSs in a fraction 0.7 per cent, 18.1 per cent, and 96.5 per cent of MW-like haloes when Tact is set to 9000, 7000, and 5000 K, respectively. For the canonical atomic-cooling threshold ( Tact 8000 K), the HSS fraction is 1per cent , indicating that Leo I hosting a heavy-seed descendant is unlikely under well-motivated physical assumptions. Higher HSS fractions occur only under optimistic and currently unsubstantiated assumptions on Tact . Nevertheless, these results motivate future work that clarifies the possibility of heavy-seed BH formation in pristine haloes with nominal virial temperatures below 8000 K. This may motivate Leo I as a target for disentangling heavy seeds from other SMBH formation mechanisms. https://research-explorer.ista.ac.at/download/23150/23164/2026_MonthNoticesRAS_Scoggins.pdf application/pdfno Oxford University Press2026 eng 0035-8711 1365-2966 2511.0473610.1093/mnras/stag1839 5523 Scoggins, Matthew T., Zoltán Haiman, and Fabio Pacucci. “Heavy Black Hole Seed Survivors in Dwarf Galaxies: A Case Study of Leo I.” <i>Monthly Notices of the Royal Astronomical Society</i>. Oxford University Press, 2026. <a href="https://doi.org/10.1093/mnras/stag1839">https://doi.org/10.1093/mnras/stag1839</a>. M. T. Scoggins, Z. Haiman, and F. Pacucci, “Heavy black hole seed survivors in dwarf galaxies: A case study of Leo I,” <i>Monthly Notices of the Royal Astronomical Society</i>, vol. 552, no. 3. Oxford University Press, 2026. M.T. Scoggins, Z. Haiman, F. Pacucci, Monthly Notices of the Royal Astronomical Society 552 (2026). Scoggins, M. T., Haiman, Z., &#38; Pacucci, F. (2026). Heavy black hole seed survivors in dwarf galaxies: A case study of Leo I. <i>Monthly Notices of the Royal Astronomical Society</i>. Oxford University Press. <a href="https://doi.org/10.1093/mnras/stag1839">https://doi.org/10.1093/mnras/stag1839</a> Scoggins, Matthew T., et al. “Heavy Black Hole Seed Survivors in Dwarf Galaxies: A Case Study of Leo I.” <i>Monthly Notices of the Royal Astronomical Society</i>, vol. 552, no. 3, stag1839, Oxford University Press, 2026, doi:<a href="https://doi.org/10.1093/mnras/stag1839">10.1093/mnras/stag1839</a>. Scoggins MT, Haiman Z, Pacucci F. 2026. Heavy black hole seed survivors in dwarf galaxies: A case study of Leo I. Monthly Notices of the Royal Astronomical Society. 552(3), stag1839. Scoggins MT, Haiman Z, Pacucci F. Heavy black hole seed survivors in dwarf galaxies: A case study of Leo I. <i>Monthly Notices of the Royal Astronomical Society</i>. 2026;552(3). doi:<a href="https://doi.org/10.1093/mnras/stag1839">10.1093/mnras/stag1839</a> 231502026-10-18T22:01:51Z2026-10-19T07:05:55Z