A stellar death reveals an intermediate-mass black hole


Astronomers have discovered a previously undetected intermediate-mass black hole in a dwarf galaxy in the moment in which swallowed a star that got too close.

With this discovery, featured in Nature Astronomyscientists hope to improve their understanding of the growth of supermassive black holes in massive galaxies.

The destruction of the star, a phenomenon known as “tidal disruption event”, it produced a flare of radiation that briefly eclipsed the combined starlight of the host dwarf galaxy and could help scientists better understand the relationships between black holes and galaxies.

The flare was captured by astronomers at the Young Supernova Experiment (YSE), a study designed to detect cosmic explosions and transient astrophysical events. The international team that authored the work was led by scientists from the University of California and Washington State University, in the United States, and the Niels Bohr Institute of the University of Copenhagen (Denmark).

“This discovery has raised great expectations because we can use tidal perturbations not only to find more intermediate-mass black holes in quiet dwarf galaxies, but also to measure their masses“, it states it’s a statement co-author Ryan Foley, an associate professor of astronomy and astrophysics at UC Santa Cruz, who helped plan the YSE study.

First author Charlotte Angus of the Niels Bohr Institute notes that the team’s findings provide a baseline for future studies of medium-sized black holes.

“The fact that we were able to capture this medium-sized black hole as it devoured a star has given us an extraordinary opportunity to detect what would otherwise have been hidden from us,” Angus explains. properties of the flare itself to better understand this elusive group of mid-weight black holes, that could account for most of the black holes at the centers of galaxies.”

Supermassive black holes are found at the center of all massive galaxies, including our Milky Way. Astronomers conjecture that these massive beasts, with millions or billions of times the mass of the sun, they could have grown from smaller “intermediate-mass” black holes with thousands or hundreds of thousands of solar masses.

One of the theories about how these massive black holes formed is that the early universe was riddled with small dwarf galaxies with intermediate-mass black holes. Over time, these dwarf galaxies would have merged or been engulfed by more massive galaxies, whose nuclei would each time combine to increase the mass at the center of the growing galaxy. This merging process would eventually create the supermassive black holes seen today.

“If we can understand the population of intermediate-mass black holes that there are — how many there are and where they are — we can help determine if our theories about the formation of supermassive black holes are correct“, says co-author Enrico Ramírez-Ruiz, professor of astronomy and astrophysics at UCSC and Niels Bohr professor at the University of Copenhagen.

It is not clear whether all dwarf galaxies have medium-sized black holes. “That’s hard to say. because detecting intermediate-mass black holes is extremely difficult“, recognizes Ramírez-Ruiz.

Classical black hole search techniques, which search for actively feeding black holes, are typically not sensitive enough to discover black holes at the centers of dwarf galaxies. Consequently, only a tiny fraction of dwarf galaxies are known to harbor intermediate-mass black holes. Finding more intermediate-mass black holes with tidal disruption events could help settle the debate over how supermassive black holes form.

“One of the biggest open questions in astronomy is how supermassive black holes form,” says co-author Vivienne Baldassare, professor of physics and astronomy at Washington State University.

Data from the Young Supernova Experiment allowed the team to detect the first signs of light as the black hole began to devour the star. Capturing this initial moment was essential to discover the size of the black hole, since the duration of these events can be used to measure the mass of the central black hole.

This method, which until now had only been shown to work well with supermassive black holes, was first proposed by Ramírez-Ruiz and co-author Brenna Mockler of UC Santa Cruz.

“This eruption was incredibly fast, but since our YSE data gave us a lot of early information about the event, we were able to pin down the mass of the black hole with itAngus explains.