You wait ages to see a colliding pair of black holes in a dwarf galaxy, and then two come at once! Astronomers have spotted not one, but two black hole duos in dwarf galaxies on separate collision courses, the first observational evidence of such a cosmic collision.
Just like them black holes They are heading for a collision and merger that will leave behind an even more massive black hole, the dwarf galaxies they also sit together and form a larger galaxy. This means the findings could have important implications for our understanding of how these cosmic titans and the galaxies they inhabit grew in ancient times universe.
Scientists studied the colliding black hole pairs using NASA’s Chandra X-ray Observatory and found that as the dwarf galaxies race toward each other, they suck in gas that ‘feeds’ their black holes, causing them to grow even before the merger.
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Dwarf galaxies are small galaxies with a stellar mass no more than about 3 billion times the mass of the stars Sun. In comparison, the entire Milky Way It is believed to contain a stellar mass about 60 billion times that of our star.
Scientists believe that for the first hundred million years after the Big Bang, the early Universe was full of these dwarf galaxies, most of which merged into larger galaxies like ours.
“Most of the dwarf galaxies and black holes in the early Universe are likely to have grown much larger by now, thanks to repeated mergers,” said Brenna Wells, a researcher at the University of Alabama at Tuscaloosa who helped observe A Opinion. (opens in new tab) “In a way, dwarf galaxies are our galactic ancestors, evolving over billions of years to give birth to large galaxies like our own Milky Way.”
These early galaxies have not been observed before because they are extremely faint and distant. However, astronomers have seen close-up dwarf galaxies in the process of merging, but until now there have been no signs of black holes in these galaxies.
“Astronomers have found many examples of black holes on collision courses in large galaxies that are relatively close together,” said Marko Micic, also a researcher at the University of Alabama at Tuscaloosa and a member of the team, in the statement. “But searching for them in dwarf galaxies is much more challenging and has so far failed.”
To meet the challenge of detecting black holes in merging dwarf galaxies, Micic and the team performed a systematic study of deep Chandra X-ray observations and then compared them to both infrared data from NASA’s Wide Infrared Survey Explorer (WISE). and optical data from the Canada-France-Hawaii Telescope (CFHT).
As the material around the black holes is heated to millions of degrees, it produces large amounts of high-energy light in the form of X-rays, which Chandra can see very well. While chasing pairs of bright X-ray sources in colliding dwarf galaxies, researchers uncovered two examples.
The next pair of colliding black holes in dwarf galaxies is at 760 million light years from Earth in galaxy cluster Abell 133. These dwarf galaxies appear to be in the later stages of mergers, with the tidal effects of the collision causing a long tail of material to form.
That tail of gas and dust prompted scientists to nickname this collision “Mirabilis,” which refers to an endangered species of hummingbird with an exceptionally long tail. They only chose a name for this collision because it is almost complete and thus effectively represents a single object.
Located about 3.2 billion light-years away in the galaxy cluster Abell 1758S, the more distant merger is in an earlier collision state. That said, the scientists gave the collision’s dwarf galaxy components two names, “Elstir” and “Vinteuil.” Both names refer to fictional artists from Marcel Proust’s In Search of Lost Time.
This more distant collision does not have a tidal tail, but it has evolved another interesting collision-related feature, a bridge of stars and dust that stretches to connect the two dwarf galaxies.
The team of astronomers will now continue to monitor these collisions to see how they occur and what impact they have on the dwarf galaxies.
“By using these systems as analogues for systems in the early Universe, we can study questions about the first galaxies, their black holes, and collisional star formation,” said Olivia Holmes, co-author of the research and astronomer from the University of Alabama.
The team’s research results are published in the Paper Repository ArViX (opens in new tab) and was accepted for publication in the Astrophysical Journal.
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