Astronomers have discovered many massive black holes in dwarf galaxies

(ORDO NEWS) — American astronomers have found that dwarf galaxies are much more likely than scientists thought to contain massive black holes at their centers. The results of their study will help to better understand the history of the supermassive black hole at the center of our galaxy.

It is believed that our galaxy was formed as a result of the merger of many dwarfs. In addition, two dwarf galaxies – satellites of the Milky Way – the Magellanic Clouds – will merge with it in the future. Each likely contains a black hole at its center, destined to be swallowed up by the Milky Way’s central supermassive black hole.

However, it was still unknown how often dwarf galaxies contain a massive black hole. This has been a key problem in understanding how galaxies merge and form supermassive black holes.

A new study by scientists from the University of North Carolina at Chapel Hill (USA) has filled this gap. Astronomers have shown that massive black holes are much more common than previously thought in dwarf galaxies. The results are published in the Astrophysical Journal.

Black holes are usually discovered while actively absorbing the gas around them and growing. This causes their intense and clearly visible glow.

However, similar high-energy radiation can also emit regions of the universe where active star formation occurs. Traditionally, astronomers have distinguished between these phenomena using various diagnostic tests based on the detailed characteristics of the emission spectra.

When the authors of the study tried to apply these methods to large-scale surveys of galaxies, they found that some of them could not be unambiguously assigned to one of the categories. Some tests indicated the presence of a growing black hole, while others indicated active star formation.

Scientists have a suspicion that these ambiguous cases may be dwarf galaxies in which star formation is taking place, but there is also a previously unknown black hole. Theoretical modeling made it possible to confirm this assumption.

Astronomers then compiled a detailed census of massive, growing black holes. It turned out that most often they are found in dwarf galaxies, in 80% of cases they also undergo active star formation.

The results of the study are extremely important for understanding the evolution of supermassive black holes, like the one at the center of the Milky Way, since the discovered black holes are their building blocks.


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