III Simposio de Postgrado 2025: Ingeniería, ciencia e innovación

01 39 Black Holes through cosmic time: Observational constraints and theoretical predictions Paula Cáceres Burgos ¹,²* Paulina Lira ¹ Pratika Dayal ² *E-mail: pcaceres@das.uchile.cl ¹ Departamento de Astronomía, Universidad de Chile ² Kapteyn Institute, University of Groningen Resumen Supermassive Black Holes (SMBHs;>10⁶ M ⊙ ) reside in the centres of most massive galaxies (>10¹⁰ M ⊙ ) [1] . When accreting their surrounding gas, they are categorised as Active Galactic Nuclei (AGN), detectable across a broad electromagnetic range - from Radio to gamma rays [2] . Understanding how SMBHs formed and grew is key to explaining how galaxies (like our own) evolved into what we observe today. Several theoretical models aim to explain the origins and early growth of SMBHs [3] , each predicting different BH demographics and gravitational wave signatures. Constraining these models requires a complete BH census, particularly in the intermediate mass regime (10³-10⁶ M ⊙ ), which remains elusive to standard AGN diagnostics [4] . Simultaneously, predictions on BH-BH merger rates are important for designing future gravitational wave observatories like the Laser Interferometer Space Antenna (LISA), which are capable of detecting BH mergers up to redshift 20. In this thesis, I combine theory and observations to address these challenges. On the theoretical side, I use a Semi-Analytical model to predict BH merger rates in light of recent findings using the James Webb Space Telescope (JWST) data [5] , which have found an unexpected abundance of low-luminosity AGNs at high-redshift (z>4). On the observational side, I select intermediate mass BH candidates from two samples of local galaxies via their fast (hourly timescale) optical variability [6] , believed to be a signature of small accretion disks around low-mass BHs. __Referencias [1] Fan, X., Strauss, M. A., Becker, R. H., et al. 2006, AJ, 132, 1171146 [2] Netzer, H. (2013). The physics and evolution of active galactic nuclei. Cambridge University Press. [3] Greene, J. E., Strader, J., & Ho, L. C. 2020, ARA&A, 58, 257 [4] Chakravorty, S., Elvis, M., & Ferland, G. 2013, MNRAS, 437, 740 [5] Matthee, J., Naidu, R. P., Brammer, G., et al. 2023, ApJ, 936, 129 [6] Arévalo, P., Lira, P., Sánchez‑Sáez, P., Patel, P., López‑Navas, E., & Churazov, E. 2023, MNRAS, 518, L15