Pre-selection of Globular Clusters for Detecting Intermediate-Mass Black Holes via Microlensing Fatimah Zahra(1), Anton Timur Jaelani (2,3,4)
1) Astronomy Master Program, FMIPA, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung 40132, Indonesia
2) Astronomy Research Group and Bosscha Observatory, FMIPA, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung 40132, Indonesia
3) U-CoE AI-VLB, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung 40132, Indonesia
4) University center of Excellence for Space Science, Technology and Innovation, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung 40132, Indonesia
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 10^2M_\odot to 10^5M_\odot. Black hole seeding theory suggests that IMBHs formed at high redshifts (z \geq 10) 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 SMBH. 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 early selection of globular cluster candidates, with aim to look further into the possibility of detecting IMBHs via microlensing. We choose globular clusters located near the direction of the Galactic Center. The selection process was based on several criteria including mass, magnitude of cluster member stars and extinction. We also calculate number of background stars. Eleven globular cluster candidates were selected by this process: Pal 6, NGC 6440, Djorg 2, NGC 6540, NGC 6544, NGC 6553, NGC 6626, NGC 6638, NGC 6642, NGC 6656 and NGC 6717.
Keywords: Intermediate-mass black hole, globular cluster, microlensing
