Astronomers have discovered a rare compact ancient galaxy hosting a supermassive black hole with an estimated mass of 2 million solar masses.
Compact dwarf galaxies, also known as dwarf ellipticals, are extremely rare in the nearby Universe. For example, in the Virgo cluster there are only a handful of possible elliptical galaxy candidates. Although an increasing number of these populations located in different environments have been reported in recent works, most of them, however, are found in dense environments, particularly around massive galaxies.
One theory explained their proximity to a massive host galaxy, favoring a scenario in which they arise through the tidal stripping of larger galaxies. So, discovereing an isolated elliptical galaxy fitting an alternative scenario other than stripping, has gained much attention in the recent literature.
Its well known that the majority of ‘big’ galaxies, including the Milky Way, hosts supermassive black holes (SMBHs) at their center. At present, the standard model said that a correlation between the masses of SMBHs and host galaxies bulge masses exists. However, there has been a debate on the universality of this relation at the low mass galaxy — as it is not conclusive whether a majority of dwarf galaxies possess BHs at their centers or not.
According to a common wisdom these galaxies are devoid of gas and have less chance of acquiring gas from external sources as massive galaxies do, thus there is no fuel left to trigger the nuclear activity. Nevertheless, the number of detection of BHs in low-mass galaxies has been increased in recent literature with the advent of large scale surveys, high precision instruments and the sophisticated modeling of the host galaxy.
In a new paper, a team of astronomers reports the discovery of an elliptical type galaxy, SDSS J085431.18+173730.5, located in a nearly-isolated environment that possesses a supermassive black hole.
Astronomers primarily made use of the SDSS-III (Sloan Digital Sky Survey) imaging data and catalog searching for low-luminosity early-type galaxies in isolated or low density environments, then they found this galaxy. SDSS J085431.18+173730.5 has a radius of roughly 1500 light years and a brightness of −18.08 mag, located 180 million light years away.
The discovery of a very compact elliptical galaxy with AGN signature might help us to explore another aspects of compact early-type galaxies.
said Sanjaya Paudel, Korea Astronomy and Space Science Institute, one of the authors of the paper.
The study was published on 17 March in the Astrophysical journals Letter.