Astronomers have discovered three merging galaxies, which are at the stage of the triple active nucleus. At the moment, supermassive holes in their centers are at a fairly large distance, but in the future they will come closer and form a tight system. The discovered object is the best known example of a rare merge.
The modern cosmological model predicts a hierarchical growth of structures in the Universe, which, in particular, is expressed in the frequent merging of galaxies, and a lot of examples of interacting pairs of galaxies are really known. One of the consequences of mutual perturbations is a sharp increase in the rate of accretion onto central black holes, due to which the surrounding material begins to glow brightly – an active galactic nucleus is formed.
One of the main unsolved problems of modern cosmology is the growth of supermassive black holes. It is known that such objects are observed in a fairly early Universe about a billion years old, and there is no theory that would give a full explanation of such a rapid mass gain.
To this end, scientists have put forward many hypotheses, among which were those that associate fast growth with a high rate of accretion in the late stages of galaxy fusion, when the distance between their centers does not exceed 10 kiloparsecs. In this case, a double active core should be formed, hidden from the observer by thick layers of dust and gas, due to which it should be the brightest in the infrared range.
As part of a project to search for pairs of merging galaxies of astrophysics from the USA, Chile and Canada, led by Ryan Pfeifle from George Mason University, a system of three interacting galaxies SDSS J084905.51 + 111447.2 was discovered, each of which shows significant activity. They are in the late stages of merging, between black holes from 3 to 7 kiloparsecs. The system itself is at redshift z = 0.077, which roughly corresponds to a distance of 250 megaparsec.
First, astronomers searched for objects in the SDSS survey with volunteers as part of the Galaxy Zoo online project . Then, for interesting candidates, infrared data obtained by the WISE space telescope was studied. If there was a noticeable signal, then this meant the presence of black holes at the stage of active absorption of the substance. To confirm the results of the galaxy, they were observed using the Chandra and NuSTAR space telescopes: they recorded an X-ray glow, and it came from three separate sources.
Processing all the data obtained, as well as using archival observations of other observatories, allowed the authors to come to an unambiguous conclusion about the presence of a triple core and, accordingly, three supermassive black holes. Modeling the spectra in different ranges made it possible to exclude alternative scenarios, such as the activity of star formation regions, radiation generated by shock waves, or radiation from a smaller number of active nuclei.
The authors call the detection of the ternary system important, because there are much fewer multiple systems than predicted by modern theory. Scientists attribute this to a large absorption in the optical range due to the large amount of matter entering the centers of galaxies. At the same time, interactions in ternary systems can radically accelerate the process of black hole fusion and overcome the so-called problem of the last parsec, that is, inefficient loss of moment by such bodies in orbits of the corresponding size. In the case of three bodies, their close passage can transfer part of the energy to one of the objects, which will become unconnected with the remaining pair and leave them, while the rest will merge in a relatively short period of time.
Previously, scientists proved the presence of a swinging jet in the system of a black hole and an ordinary star, made a reliable estimate of the mass of the largest black hole, first saw the birth of a black hole and recorded a flash of activity of a supermassive black hole in the center of the Milky Way.
Via | arXiv