Supermassive black holes grow a lot in small but massive isolated galaxies

MRK 1216
MRK 1216

An article to be published in the journal “Monthly Notices of the Royal Astronomical Society” describes a research on isolated galaxies with a mass similar to the first elliptical galaxies but much smaller in which the central supermassive black hole inhibited stellar formation and grew more than normal. A team of researchers used data collected by NASA’s Chandra X-ray Observatory to examine the galaxies MRK 1216 and PGC 032873, nicknamed red nuggets, relics of the first massive galaxies that formed in the first billion years after the Big Bang.

The MRK 1216 galaxies – in the top image (X-ray: NASA/CXC/MTA-Eötvös University/N. Werner et al.; Optical: NASA/STScI) seen at visible light frequencies by the Hubble Space Telescope and at X-rays by the Chandra observatory – and PGC 032873 are respectively 295 and 344 million light years away from Earth, so in astronomical terms they’re relatively close.

The first galaxies of the type known as red nuggets that were found were billions of light years away from the Earth, making it much more difficult to study them in detail. Most galaxies of that type have gone through merger processes that changed them considerably but there are still some that remained isolated so we can see their evolution without external interference.

A team of researchers coordinated by the Mta-Eötvös University Lendület in Budapest, analyzed observations made with the Chandra X-ray observatory to examine the galaxies MRK 1216 and PGC 032873 discovering the out-of-the-ordinary size of the supermassive black holes at their center and the influence they have on star formation in those two galaxies.

In both the red nugget galaxies that were studied there’s an active galactic nucleus because there’s a lot of gas around the supermassive black hole that gets heated enough to emit strong electromagnetic radiation including the X-rays detected by Chandra. The bottom image (NASA/CXC/M.Weiss) shows an artistic illustration of that situation with materials that are partly redirected outwards at very high speeds due to the very strong gravitational and magnetic fields. That process prevents interstellar gas from cooling off enough to form new stars.

Because of their isolation, only the gas that forms the halo surrounding these galaxies provides new materials for growth. The activity of the supermassive black hole in those relatively small galaxies increases its growth abnormally. For example, the mass of the one in the center of the galaxy MRK 1216 is estimated at about 5 billion times the Sun’s, more than a thousand times that of the supermassive black hole at the center of the Milky Way.

The model that explains this growth is called “chaotic cold accretion” (CCA). In very simple words, a kind of gas rain is formed that condenses outside the hot galaxy halo and is attracted by the supermassive black hole, increasing its mass quickly and feeding the active galactic nucleus.

The influence of supermassive black holes on star formation and other influences on the galaxies that host them have been the focus of a lot of research over the last few years. Instruments such as Chandra allow to study the electromagnetic emissions around them to better understand their extreme activities.

Artist's illustration of the active galactic nucleus in MRK 1216
Artist’s illustration of the active galactic nucleus in MRK 1216

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