Astronomers from the Main Astronomical Observatory of the National Academy of Sciences of Ukraine and Kyiv National University named after. T.G. Shevchenko, and a Ukrainian student from Northwestern University in the USA discovered three new galaxies with polar rings.
New galaxies with polar rings
Ukrainian astronomers discovered three new galaxies with polar rings, using machine learning methods with an extremely small training sample. This was reported by the authors of the study to Universe Space Tech.
The results of the research will be published in the authoritative scientific journal Astronomy and Astrophysics. The article has passed all stages of work with the editors and is already waiting for publication. Her text available on the website edition.
Similar galactic systems have been known since the late 1970s. The central galaxy belongs to the class of early galaxies (elliptical or lenticular), a ring, which rotates at an angle to the central part, has the characteristics of a late galaxy (spirals, or irregular).
The formation of galaxies with a polar ring remains not fully understood. Currently, the scientific community offers three theories. One of them says, that such a system is the result of the merger of two galaxies of different sizes. Namely, when a larger galaxy does not absorb a smaller one, and the smaller one forms a ring around the larger one at a certain confluence angle.
In the second theory, two galaxies of different sizes also interact, but the matter does not come to a merger, simply the larger of them pulls the substance away from the smaller one (accretion of matter from one galaxy to another occurs), as a result of which a ring is formed. According to the third theory, rings are formed by overflow (accretion) of cold gas along cosmological filaments, causing the polar ring to form.
Galaxy SDSS J140644.42+471602.0
A team of Ukrainian scientists including Daria Dobrycheva, Oleksandr Hetmantsev, Iryna Vavilova, Oleksandr Gugnin, Andrii Shportko and Olena Kompaniets used machine learning methods to search for galaxies with polar rings. The uniqueness of this study is that, that the training sample of galaxies consisted of 87 objects, which is extremely small for this task. Given the complexities, scientists managed to discover a new galaxy with a polar ring - SDSS J140644.42+471602.0. Together with it, two more similar systems were discovered, one of them (SDSS J095717.30+364953.5) is important and can be a confirmation of the first or second theory of the formation of such unique objects, because there is fusion in it.
Scientists carried out a detailed multiwavelength study of the object SDSS J140644.42+471602.0, using data from the Sloan Digital Sky Survey (SDSS) combined with infrared observations from the WISE satellite and ultraviolet observations from the GALEX satellite.
To analyze these data, scientists used the CIGALE software package (Code Investigating GALaxy Emission). This is a modern tool, which allows to reproduce the energy "portrait" of galaxies - their spectral distribution from the ultraviolet to the infrared range - to determine their key characteristics and, on this basis, to reproduce the history of star formation.
Thanks to this approach, it was possible to find out, what is close 500 millions of years ago, this galaxy experienced a powerful burst of star formation. Ukrainian researchers came to a conclusion, that the most likely scenario for the appearance of the polar ring in SDSS J140644.42+471602.0 was accretion of matter from a companion galaxy. Since no such object can be observed near it, most likely, it was completely destroyed by this process.
Catalog of galaxies with polar rings
To search for such unique objects and apply machine learning methods, a group of Ukrainian scientists carried out extensive work on the revision of current catalogs of galaxies with polar rings. Currently, there are three catalogs of galaxies with polar rings in the literature, which were created by various authors in 1990, 2011, 2019 years. Before that, so that the machine learning algorithm starts looking for such objects, it must be taught, that is, show as many examples as possible, what kind of galaxies are these and what is their shape. For this, our scientists collected all available galaxies with polar rings from all current catalogs, they turned out 463 objects. They conducted a visual inspection of them and it turned out, that's all 87 galaxies are galaxies with polar rings, all others were rejected. But why did all other galaxies get into these catalogs before?? Our scientists explain this by, that earlier telescopes did not have such a high-quality image compared to modern ones, and the shapes of those galaxies resembled galaxies with polar rings, that's why they got into the catalogs.
In general, 87 galaxies for training a neural network is an extremely small training sample. However, Ukrainian researchers still managed to apply machine learning methods for data processing. The result was the creation of a directory, containing 167 galaxies. It can be used for further research on that, how the polar rings are formed.
Source: https://universemagazine.com