Russian astronomers have shown that the gravitational interaction of galaxies can lead to the release of the remnants of one of them from the interaction region. In this way they explained the existence of single compact elliptical galaxies.
In the universe found a huge number of galaxies of various sizes and masses. If the directory John Herschel in 1862 kept them around 5000, the orbiting telescope “Hubble” in just three and a half months have found about 10,000 galaxies scanning area of the sky a hundred times smaller than the lunar disk. This allows us to estimate the number of galaxies in the observable space, at least $ 200 billion.
A compact elliptical galaxy M 32.
The scheme of the emergence of” fluent “galaxy. Spiral galaxy on the left – “attacker” approaches (red arrow) to the cluster, where the compact elliptical galaxy (CE) has revolved around a massive central elliptical galaxy. In the center shows
colliding galaxies “Mouse» (NGC 4676A and NGC 4676B), «tail” – the release of substances (Photo telescope “Hubble»).
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Note Russian astronomers Chilingarian Igor and Ivan Zolotukhin from the Astronomical Institute of the PK Sternberg (SAI), Moscow State University (the first of which is also the US Harvard-Smithsonian Center for Astrophysics, and the second – the French Institute of Astrophysics and Planetology) drew a rare class of galaxies, so-called compact elliptical galaxies. They are characterized by small size and high stellar density. Their size is only a few hundred light-years, more star clusters, but less than a typical galaxy. For comparison, our galaxy – the Milky Way has a diameter of 100,000 light years. Compact elliptical galaxies and have a mass about 1000 times smaller than the Milky Way.
In the sky they look like stars. By 2006, it was known only 6 of these galaxies. In 2009 Chilingarian found another 20 such galaxies. Thanks to the research of the authors of today their number reached 195.
stellar density in galaxies should decrease strongly on their outskirts, which was not observed in the compact galaxies. However detected compact galaxies located near the other, larger galaxies, which allowed them to explain the formation of the gravitational interaction of galaxies, resulting in a large galaxy in a couple of billion years selects outlying stars have smaller, leaving her just enough compact central part – the core. Scientists call this process by peeling tidal. It should be noted that the interaction of galaxies – a phenomenon often enough. Some scientists believe that through it passed almost all galaxies.
But in 2013 opened two separate compact elliptical galaxies for which it was impossible to specify the galaxies that their “robbed”. The authors, a lot of work to process the available data, brought the number of such isolated galaxies to 11. All of them are located in several million light-years from the nearest galaxy clusters. Earlier in their areas just were not looking. Accordingly, there was a question about their origin.
Studies have shown that the properties of isolated compact galaxies do not differ from those that are inside the clusters. Therefore, astronomers have suggested that they have the same origin. After analyzing the same driving dynamics of galaxies, they found that isolated galaxies are moving much faster than their counterparts in clusters. This led them to conclude that the exclusion is due to the fact that these galaxies were thrown out of the interaction region as a result of the so-called gravitational interaction of three bodies.
In this case, it is that the first massive galaxy peels outer regions faced with her small galaxy, leaving it only compact nucleus, and then running at around a third galaxy sling is the core of extragalactic space. Supports this hypothesis and the nature of the movement of some compact elliptical galaxies within clusters, which indicates that they are already on the brink of relegation. The efficiency hypothesis is confirmed by numerical simulation.
Such a mechanism is not something new in astrophysics. Before that it was used to explain the two dozen runaway stars in our galaxy and even whole fleeing star clusters in the galaxy M 87. There is an assumption about the tens of billions of planets, thereby separated from their stars and wandering in space. But the first time it was applied to the entire galaxy.
«This is a manifestation of the same phenomenon at different scales of the universe – the effect of the sling when the interaction of three bodies lighter flies out of the system,” – said Zolotukhin.
Note that if the star in order to run away from home galaxy is necessary to develop a speed of about 500 km / s, the galaxy fluent it requires not less than 2500 km / s.
The results of this work are published in the journal Science.
It is possible that the compact galaxies will shed light on the evolution of galaxies and the universe, because scientists believe that they are composed of mysterious dark matter, fastening most other galaxies.
It is interesting that in his studies, astronomers used the existing observational material is placed in the public domain on the Internet under the “Virtual Observatory”. It showed integrity of the project, and now, in principle, anyone can explore the data and make a discovery in astronomy.
Fig. 2. Scheme of the emergence of “fluent” galaxy. Spiral galaxy on the left – “attacker” approaches (red arrow) to the cluster, where the compact elliptical galaxy (CE) has revolved around a massive central elliptical galaxy. In the center shows the moment a close encounter and receiving CE gravitational impact on the offender. Right CE runs away from clusters of galaxies, and the violator “consumed” by the central giant elliptical galaxy.
Based on materials from the Moscow State University and the Harvard-Smithsonian Center for Astrophysics
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