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important11-15_en


The most important scientific achievements for 2011–2015
 

1) Studying distributions of stars of different ages in irregular and spiral galaxies we found for each galaxy a clear correlation between the age of stars and the spatial size of the subsystems of stars of this age. We believe that the dependency found by us can be explained by the hypothesis of galaxy expansion over time.

Tikhonov N., Galazutdinova O., AA Transac., V. 27, Iss.2, 227, 2012.
Tikhonov N., Galazutdinova O., Astronomy Letters, V. 38, Iss.3, p. 147, 2012.
Тихонов Н.А., Astronomy Letters, V. 38, Iss.8, p. 497, 2012.
Тихонов Н.А., Astronomy Letters, V. 39, Iss.5, p. 298, 2013.

PGC9962

Fig. 1. HST image of the PGC9962 galaxy (on top). Hertzsprung-Russell diagram for this galaxy is shown with isochrones of different ages (in the bottom left corner) and number density distribution diagrams for stars of different ages perpendicular to disk plane (in the bottom right corner). The numbers on the diagrams denote the age of stars in millions of years.

2) The NGC 1313 galaxy, being, perhaps, the most mysterious galaxy of the sky, has been studied based on the Hubble Space Telescope images. In normal images, it looks like a normal spiral galaxy but deep images show that the galaxy is highly distorted by gravitational interaction. However, the images do not show any neighboring galaxy, which would create the deformation of a stellar structure. We made a stellar photometry of eight NGC 1313 fields and of its dwarf companion AM 0319-662 and studied the visible distribution of stars of different ages and of metallicity in the galaxy. It has been found that the spatial distribution of low metallicity stars is substantially different from the distribution of high metallicity stars. This distinction has allowed us to identify the fragments of a dwarf galaxy destroyed by now, being almost merged with NGC 1313. This disappeared galaxy was the cause of the gravitational deformation of NGC 1313.

Tikhonov N., Galazutdinova O., Astronomy Letters, submitted in 2015.
NGC1313

Fig. 2. Galaxy NGC 1313 (image made with 8 meter  telescope (VLT)).


3) We have developed the new method for determining the size of groups and clusters of galaxies from cumulative distribution of number of galaxies in dependence on squared clustercentric distance. For 29 systems of galaxies we have determined dynamical masses within the effective radius Re which are about 1.65 times less then masses enclosed within R200 radius. A comparison of the inferred dynamical masses and the hydrostatic masses determined from the radiation of hot gas in galaxy groups and clusters (based on published data) led us to conclude that the inferred masses for the main sample of 21 groups and clusters, which does not include merging clusters with irregular structure, the dynamical masses exceed the X-ray masses an average by 12%, with an rms scatter of 35%.

         Kopylov A.I., Kopylova F.G., Ast. Bull., 70, 243, 2015.

fig1

        Fig. 3. A comparison of the X-ray masses (MX,200) obtained by gas radiation in X-ray band with the dynamical masses (M200) measured from the radial velocities of galaxies. The objects of the main sample are shown by filled circles.