Active nucleus of the galaxy NGC 2992 reveals its secrets

(ORDO NEWS) — The researchers conducted joint observations of an active galactic nucleus (AGN) called NGC 2992 using the Very Long Baseline Array (VLBA) radio observatory and NASA’s Swift spacecraft. These results help to better understand the properties of this AGN and its host galaxy.

AGNs are accreting supermassive black holes lying in the centers of some galaxies, in the vicinity of which powerful streams of high-energy radiation are formed as a result of accretion of gas and dust. These nuclei can form jets that are observed even at scales of the order of megaparsecs.

NGC 2992, about 103 million light-years from Earth, is a Sa-type Seyfert galaxy because it is a spiral galaxy without a central bar. The galaxy NGC 2992 is characterized by particularly high X-ray variability, showing changes in luminosity in observations in the range of 2-10 kiloelectronvolts (keV) at a level of more than one order of magnitude over several days or weeks.

At the center of the galaxy NGC 2992 lies a powerful AGN, whose activity is probably associated with the influence of the neighboring galaxy, NGC 2993. These two galaxies are connected by a tidal bridge of ionized hydrogen, and tidal tails.

In a new paper, a team led by Luis C. Fernandez of the US Naval Observatory conducted joint X-ray and radio observations of the AGN of the galaxy NGC 2992 in order to evaluate the mutual dependence of the source’s luminosity in these two bands.

As a result of the observations, the authors found an inverse correlation between the radio emission of the nucleus (at a frequency of 6 gigahertz) and its X-ray emission (2-10 keV). Radio emission decreased by more than a factor of three shortly after the X-ray flares. The researchers also found that the size of the area from which radio emission is observed corresponds to the central accretion region.

Astronomers believe that the observed radiation from the nucleus of the galaxy NGC 2992 in the X-ray and radio bands is probably associated with flares that cause the occurrence of magnetic reconnection events in the accretion disk. These events form bursts of Comptonized plasma, resulting in an increase in the overall brightness of the source in hard X-rays, they added.

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