New research has uncovered a significant number of black holes, possibly solving a major cosmic mystery. Astronomers recently identified 2,444 active black holes nestled in the centers of dwarf galaxies scattered across the universe. Remarkably, 298 of these black holes fall into the category of intermediate mass black holes (IMBHs) – a type that has long eluded scientists.
This discovery triples the number of confirmed IMBH candidates so far. Understanding these black holes is crucial because they are key to explaining how black holes grow to sizes comparable to millions or even billions of suns.
Supermassive black holes are found at the heart of large galaxies, like the one at the center of our Milky Way, which is 4.3 million times the mass of the Sun. However, scientists are puzzled about how these massive entities form. Theories suggest they could grow by accumulating matter over time or by merging with other black holes. Unfortunately, our current technology struggles to detect the smaller “seed” black holes from the early universe due to their faintness.
Instead, researchers have focused on smaller galaxies that may contain smaller black holes nearby. Led by Ragadeepika Pucha from the University of Utah, a team used the Dark Energy Spectroscopic Instrument (DESI) to survey the universe. In its first year, DESI analyzed 114,496 dwarf galaxies, allowing astronomers to identify signs of black holes actively consuming matter, known as active galactic nuclei.
The findings are impressive. Out of the observed dwarf galaxies, 2,444 showed signs of active galactic nuclei, which is nearly four times the percentage discovered in previous surveys. This indicates that there may be far more low-mass supermassive black holes in the universe than we previously thought.
From their observations, scientists estimated the masses of the black holes they examined, identifying almost 300 IMBH candidates, with masses ranging from about 100 to 100,000 times that of the Sun. Finding black holes in this mass range is significant because they are rare and can help explain how smaller black holes evolve into supermassive ones.
One important aspect of black holes is that they can merge, leading to the formation of larger black holes. A robust sample of IMBHs could help clarify how this merging process occurs and how it leads to the creation of enormous black holes.
The new research produced 151 certain IMBH candidates and an additional 147 that are merely tentative. This more than doubles the previous count of candidates, which was only around 100 to 150. Interestingly, most of the newly identified IMBH candidates were found in regular galaxies rather than dwarf galaxies. This discovery suggests that the relationship between black holes and galaxies is more complex than previously thought.
There’s still much to learn. The early data from DESI offers just a glimpse of what lies ahead. With more findings, astronomers hope to investigate questions like how the formation of black holes might relate to the types of galaxies they inhabit.
The results of this research can be found in The Astrophysical Journal.
