Pre-selection of Globular Clusters for Detecting Intermediate-Mass Black Holes via Microlensing

Authors

  • Fatimah Zahra Astronomy Master Program, FMIPA, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung 40132, Indonesia
  • Anton Timur Jaelani Astronomy Research Group, FMIPA, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung 40132, Indonesia

DOI:

https://doi.org/10.21009/SPEKTRA.111.02

Keywords:

intermediate-mass black hole, globular cluster, microlensing, Gaia DR3, background star density

Abstract

Intermediate-mass black holes (IMBHs) are the key to understanding the formation of supermassive black holes (SMBHs) that are typically found in centers of massive galaxies. In general definition, IMBHs are black holes masses ranging from 102 M⨀ to 105 M⨀. Black hole seeding theory suggests that IMBHs formed at high redshifts (z ≥ 0) through gravitational collapse of Population III stars, direct collapse of protogalaxy clouds, or stellar collisions inside high-density clusters. These IMBHs evolve into SMBHs through accretion and mergers. However, not all of these IMBHs are successful in forming SMBHs. Those that fail are hypothesized to be observable in the local universe, particularly in globular clusters and dwarf galaxies. IMBHs have yet to be definitively detected, however several strong candidates have been located in the cores of globular clusters. This study describes the preliminary selection stage of globular cluster candidates with the aim to look further into the possibility of detecting IMBHs via microlensing. The selection process was based on several physical properties of the globular clusters including mass, metallicity, and central velocity dispersion. Since background star density strongly affects microlensing detection probability, we restricted the sample to clusters located in the direction of the Galactic center. We utilized Gaia DR3 data to estimate background star density for selected globular clusters using proper motion filtering and Theil-Sen regression method. These estimates provide the foundation for further subsequent simulations of microlensing detection probabilities associated with central IMBHs.

References

J. E. Greene, J. Strader, and L. C. Ho, “Intermediate-Mass Black Holes,” Annual Review of Astronomy and Astrophysics, vol. 58, pp. 257–312, 2020, doi: 10.1146/annurev-astro-032620-021835

A. Heger and S. E. Woosley, “The Nucleosynthesis Signature of Population III,” The Astrophysical Journal, vol. 567, pp. 532–543, 2002, doi: 10.1086/338487

B. Paczyński, “Gravitational Microlensing by the Galactic Halo,” The Astrophysical Journal, vol. 304, pp. 1-5, 1986, doi: 10.1086/164140

R. A. Remillard and J. E. McClintock, “X-Ray Properties of Black-Hole Binaries,” Annual Review of Astronomy and Astrophysics, vol. 44, pp. 49–92, 2006, doi: 10.1146/annurev.astro.44.051905.092532

W. R. Brown, “Hypervelocity Stars,” Annual Review of Astronomy and Astrophysics, vol. 53, pp. 15–49, 2015, doi: 10.1146/annurev-astro-082214-122230

Event Horizon Telescope Collaboration, K. Akiyama, A. Alberdi, et al., “First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way,” The Astrophysical Journal Letters, vol. 930, 2, p. L12, 2022, doi: 10.3847/2041-8213/ac6674

M. J. Rees, “Black Hole Models for Active Galactic Nuclei,” Annual Review of Astronomy and Astrophysics, vol. 22, pp. 471–506, 1984, doi: 10.1146/annurev.aa.22.090184.002351

J. F. W. Baggen, P. van Dokkum, I. Labbé, et al., “Sizes and Mass Profiles of Candidate Massive Galaxies Discovered by JWST at 7 < z < 9: Evidence for Very Early Formation of the Central 100 pc of Present-day Ellipticals,” The Astrophysical Journal Letters, vol. 955, 1, p. L12, 2023, doi: 10.3847/2041-8213/acf5ef

E. Vasiliev and H. Baumgardt, “Gaia EDR-3 View on Galactic Globular Clusters,” Monthly Notices of the Royal Astronomical Society, vol. 505 4, pp. 5978–6002, 2021, doi: 10.1093/mnras/stab1475

N. Kains, D. M. Bramich, K. C. Sahu, and A. Calamida, “Searching for Intermediate-Mass Black Holes in Globular Clusters with Gravitational Microlensing,” Monthly Notices of the Royal Astronomical Society, vol. 460, 2, pp. 2025–2035, 2016, doi: 10.1093/mnras/stw1137

M. Volonteri, “Formation of Supermassive Black Holes,” Astronomy and Astrophysics Review, vol. 18, 3, pp. 279–315, 2010, doi: 10.1007/s00159-010-0029-x

K. Sharma and C. L. Rodriquez, “From Young Massive Clusters to Old Globular Clusters: Density Profile Evolution and Intermediate-Mass Black Hole Formation,” The Astrophysical Journal, vol. 983, 2, id. 162, 2025, doi: 10.3847/1538-4357/adbbdf

M. Dominik and K. C. Sahu, “Astrometric Microlensing of Stars,” The Astrophysical Journal, vol. 534, 1, pp. 213–226, 2000, doi: 10.1086/308716

M. Servillat, S. A. Farrell, D. Lin, et al., “X-Ray Variability and Hardness of ESO 243-49 HLX-1: Clear Evidence for Spectral State Transitions,” The Astrophysical Journal, vol. 743, 1, pp. 1-12, 2011, doi: 10.1088/0004-637X/743/1/6

S. Kamann, L. Wisotzki, M. M. Roth, et al., “The Central Dynamics of M3, M13, and M92: Stringent Limits on the Masses of Intermediate-Mass Black Holes,” Astronomy and Astrophysics, vol. 566, A58, pp. 1-24, 2014, doi: 10.1051/0004-6361/201322183

M. Mezcua, “Observational Evidence for Intermediate-Mass Black Holes,” International Journal of Modern Physics D, vol. 26, 11, id. 1730021, 2017, doi: 10.1142/S021827181730021X

H. Baumgardt, J. Makino, and P. Hut, “Which Globular Clusters Contain Intermediate-Mass Black Holes?” The Astrophysical Journal, vol. 620, 1, pp. 238-243, 2005, doi: 10.1086/426893

N. Kains, A. Calamida, K. C. Sahu, et al., “A Search for Black Hole Microlensing Signatures in Globular Cluster NGC 6656 (M22),” The Astrophysical Journal, vol. 867, 1, id. 37, 2018, doi: 10.3847/1538-4357/aae311

Z. Wu and L. C. Ho, “Detecting Intermediate-mass Black Holes Using Quasar Microlensing,” The Astrophysical Journal, vol. 985, 2, id. 197, 2025, doi: 10.3847/1538-4357/adcec3

A. T. Bajkova, A. A. Smirnov, and V. V. Bobylev, “Analysis of Orbital Dynamics of Globular Clusters in the Central Region of the Milky Way,” Astrophysical Bulletin, vol. 80, pp. 369–393, 2025, doi: 10.1134/S1990341325600310

M. S. Fujii, L. Wang, A. Tanikawa, et al., “Simulations Predict Intermediate-Mass Black Hole Formation in Globular Clusters,” Science, vol. 384, 6703, pp. 1488–1492, 2024, doi: 10.1126/science.adi4211

H. Baumgardt and M. Hilker, “A Catalogue of Masses, Structural Velocity Dispersion Profiles of 112 Milky Way Globular Clusters,” Monthly Notices of the Royal Astronomical Society, vol. 478 2, pp. 1520–1557, 2018, doi: 10.1093/mnras/sty1057

P. Schneider, J. Ehlers, E. E. Falco, "Gravitational Lenses", Berlin: Springer, 1992, doi: 10.1007/978-3-662-03758-4

Y. Tsapras, Y., “Microlensing Searches for Exoplanets,” Geosciences, vol. 8, 10, id. 365, 2018, doi: 10.3390/geosciences8100365

W. E. Harris, “A Catalog of Parameters for Globular Clusters in the Milky Way,” The Astronomical Journal, vol. 112, p. 1487, 1996, doi: 10.1086/118116

B. Kızıltan, H. Baumgardt, and A. Loeb, “An Intermediate-Mass Black Hole in the Centre of the Globular Cluster 47 Tucanae,” Nature, vol. 542, pp. 203–205, 2017, doi: 10.1038/nature21361

Published

2026-04-30

How to Cite

Zahra, F., & Jaelani, A. T. (2026). Pre-selection of Globular Clusters for Detecting Intermediate-Mass Black Holes via Microlensing. Spektra: Jurnal Fisika Dan Aplikasinya, 11(1). https://doi.org/10.21009/SPEKTRA.111.02

Issue

Vol. 11 No. 1 (2026): SPEKTRA: Jurnal Fisika dan Aplikasinya, Volume 11 Issue 1, April 2026

Section

Articles

License

Copyright (c) 2026 Fatimah Zahra, Anton Timur Jaelani

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 International License.

SPEKTRA: Jurnal Fisika dan Aplikasinya allow the author(s) to hold the copyright without restrictions and  allow the author(s) to retain publishing rights without restrictions. SPEKTRA: Jurnal Fisika dan Aplikasinya CC-BY or an equivalent license as the optimal license for the publication, distribution, use, and reuse of scholarly work. In developing strategy and setting priorities, SPEKTRA: Jurnal Fisika dan Aplikasinya recognize that free access is better than priced access, libre access is better than free access, and libre under CC-BY or the equivalent is better than libre under more restrictive open licenses. We should achieve what we can when we can. We should not delay achieving free in order to achieve libre, and we should not stop with free when we can achieve libre.

SPEKTRA: Jurnal Fisika dan Aplikasinya is licensed under a Creative Commons Attribution 4.0 International License.
You are free to:
Share - copy and redistribute the material in any medium or format
Adapt - remix, transform, and build upon the material for any purpose, even commercially.
The licensor cannot revoke these freedoms as long as you follow the license terms.