At Moscow State University have developed an efficient method of study distant galaxies


Employees of the State Astronomical Institute of the PK Sternberg State University (SAI) Chilingaryan Igor and Ivan Zolotukhin, processed through the Virtual Observatory data on 200,000 galaxies have invented a technique that allows to determine the structure of distant galaxies, their distance and other important parameters are literally on the three images.

Astrophysical objects can not be directly touched or involved in the experiments. Their physical properties, and distance to them can be judged or from direct observations, or indirect evidence.

Modern telescopes can detect galaxies at such large distances, which is very difficult not only to investigate the structure, but also to fix even such powerful emission energy as a supernova explosion, not to mention the fact that the study Cepheids. Images of distant galaxies obtained by ground-based telescopes, is not sufficient to determine their morphological types and estimates of the distances to them. These tasks require the use of additional data, such as live images and high-resolution spectroscopic observations obtained with the Space Telescope. But now astronomers know many millions of galaxies — it is clear that it is physically impossible to observe each of them into space telescope "Hubble".

However, some information about the morphology of galaxies can be produced based on the results of photometric observations, as the color of a single galaxy is related to its morphological type and is primarily determined by the history of star formation in it. In 2001, the results of a large-scale work, when a group of scientists led by Spark Stratevoy (Germany) published the results of the analysis of almost 150,000 images of galaxies obtained during the review of Sloan Digital Sky Survey (SDSS). For these galaxies was constructed chart, linking the color indices of the galaxies in the optical (using the difference of flow in the filter g, ie, the green region of the spectrum, and r, red region of the spectrum) with the luminosity of the galaxy. In this diagram, identified two distinct regions. The first — the "red sequence» (Red sequence), which consists mainly of older galaxies, elliptical and lenticular, where there are no areas of current star formation. Another area — "blue cloud» (Blue cloud), which inhabit mainly the younger spiral galaxies where star formation takes place in the present.

It would seem that using such a chart, you can, getting the color indices of the observations of the galaxy and its magnitude, immediately determine which morphological type it is, what her structure, how old she is, etc. But for a complete classification of galaxies this chart can not be used due to a number of problems. To avoid them, the Russian astronomers Chilingaryan Igor and Ivan Zolotukhin, in addition to working in the Sternberg Astronomical Institute at the Harvard-Smithsonian Center for Astrophysics (USA) and the Observatoire de Paris (France), respectively, have made such a chart is not flat and three-dimensional and add the color indices in the near-ultraviolet. Scientists have used a virtual observatory for the construction of the multi-wavelength catalog of galaxies by cross-identification of objects in three large photometric surveys: NASA Galaxy Evolution Explorer (UV range), Sloan Digital Sky Survey (optical range) and the UK Infrared Telescope Deep Sky Survey (near infrared). "We have compiled a catalog of more than 200,000 galaxies. After that, we have carefully studied what we’ve got, — Says Ivan Zolotukhin — and found that the vast majority of these galaxies have a connection between the color indices in the optical and ultraviolet, as well as the luminosity and all of it is also related to the properties of galaxies and their morphology. It is widely used by astronomers figure "in the optics of color — magnitude" we have added another dimension — "the color in the ultraviolet." If the galaxies in the two-dimensional plane broke into two significant areas, in three-dimensional space, they unexpectedly went along fine smooth surface, pointing to a new, yet incomprehensible law. "

"Our work will allow astronomers to classify millions of galaxies, and to determine their distances, using only their image, — Igor Chilingaryan. — For distant galaxies, the structure of which we can not see directly, it is now possible to determine their morphological type (that is, to know whether the star system is a spiral or elliptical), but measuring their flow. Another advantage of our study is that now be easily identified members of rare galaxy types (such as, for example, compact ellipticals) as they are located apart on our three-dimensional diagram. The physical nature of an open us closer photometric dependence is not yet clear — it is a new challenge for theorists and researchers involved in the numerical simulation of the evolution of galaxies. "

The publication is published in the journal Monthly Notices of the Royal Astronomical Society. With work can be found on the website and preprints by the press service of the Moscow State University

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