Little Red Dots and the Birth of Black Holes
Little Red Dots (LRDs), discovered by JWST, are extremely dense, compact galaxies seen early in the universe. Andrés Escala and collaborators show that, under the “stellar-only” view, their extreme densities make them unstable and prone to runaway star collisions. No matter the scenario, whole system collapse, shrinking sizes, or collapsing cores, the likely fate of LRDs is to form massive black holes, making them prime sites to study black hole seeds in formation.
A Stellar Blender: Black Holes May Be Pulverizing Stars at the Center of the Milky Way
Haas et al. propose that a dense cluster of stellar-mass black holes near the Milky Way’s center acts as a “star grinder,” destroying massive stars through collisions. This explains the absence of O-type stars in the S-cluster and matches observed star distributions. Their model also accounts for missing hypervelocity star counterparts and supports a peaked black hole density near Sgr A⋆.
Exploring the Invisible: Searching for Primordial Black Holes in the Milky Way
A study led by Przemek Mróz used the OGLE survey to search for primordial black holes (PBHs) as dark matter candidates in the Milky Way. Analyzing 20 years of data from 80 million stars, the team found no long-timescale microlensing events, placing strict limits on the contribution of PBHs to dark matter. These findings challenge theories linking PBHs to dark matter or black hole merger rates observed by gravitational wave detectors.
Exploring Black Holes in Dwarf Galaxies: Insights from Omega Centauri
This study by Limberg explores the proposed intermediate-mass black hole (IMBH) in Omega Centauri (ωCen), a stripped nuclear star cluster thought to be from the dwarf galaxy Gaia-Sausage/Enceladus. It extends known relationships between black hole mass, stellar mass, and velocity dispersion to dwarf galaxies, suggesting such galaxies follow similar evolutionary patterns as larger systems. The findings emphasize the importance of studying IMBHs to understand black hole formation and their role in galaxy evolution.
Formation of Star Clusters and Black Holes in the Early Universe: Insights from High-Redshift Galaxies
Lucio Mayer and colleagues used high-resolution simulations to investigate the formation of ultra-compact star clusters and massive black holes in early galaxies at redshifts greater than 7. They found that dense, gas-rich disks in these galaxies could fragment, rapidly forming compact star clusters with extreme stellar densities. The team suggests that these clusters could generate intermediate-mass black holes, which would then merge to form supermassive black holes, explaining the overmassive black holes observed by JWST in the early universe.
Mapping the Gravitational Wave Background: Unveiling Cosmic Structures with Black Hole Mergers
This study by Semenzato and colleagues investigates how gravitational waves from supermassive black hole binaries might reveal patterns in the universe's large-scale structure (LSS). Using simulations, they show that filtering out loud sources uncovers a gravitational wave background (GWB) that aligns with galaxy clustering, suggesting that the GWB could serve as a cosmic map of LSS. They conclude that cross-correlating GWB maps with galaxy distributions in future pulsar timing array experiments could offer unique insights into the structure of the universe and the distribution of dark matter.