Current Issues

Communications of the Byurakan Astrophysical Observatory (ComBAO)
Volume LXV, Issue 2, December 2018


Editor's Introduction 0.08 MB
H. A. Harutyunian
Pages: 160-161



Viktor Ambartsumian’s most important achievements 0.4 MB
A. M. Mickaelian
Pages: 162-183
Abstract. We give a review of the most important scientific achievements of one of the greatest scientists of the XX century, the founder of the modern astrophysics in Armenia, Viktor A. Ambartsumian (1908-1996). He has fundamentally contributed in various fields of astronomy and astrophysics, cosmogony, theoretical physics, mathematics, and philosophy. We list the most important scientific results, including his revolutionary works on origin and evolution of stars and activity of galactic nuclei that turned over the development of astrophysics and gave life to our before unchanged Universe. He was one of the founders of the theory of planetary nebulae, stellar dynamics, protostellar dense matter, as well as he has contributed in other important areas of the theoretical astrophysics. Ambartsumian was also a great organizer of science, important political and public figure. He was the founding Director of the Byurakan Astrophysical Observatory (BAO, 1946-1988), the President of the Armenian Academy of Sciences in 1947-1993, the President of the International Astronomical Union (IAU) in 1961-1964 and the President of the International Council of Scientific Unions (ICSU) in 1968-1972. He was the founder of the theoretical astrophysics in the Soviet Union, the founder of chairs of astrophysics in Leningrad (St. Petersburg) and Yerevan state universities, as well as the journals Communications of BAO and Astrofizika (Astrophysics).


Part I. Stars and Nebulae

Toward understanding of the origin of the B[e] phenomenon in FS CMa type objects 0.3 MB
A. S. Miroshnichenko
Pages: 184-192
Abstract. Large amounts of circumstellar material accompany lives of most stars at different evolutionary stages. Formation mechanisms of these, often disk-like envelopes are not always clear. The B[e] phenomenon includes the presence of permitted and forbidden line emission and strong infrared (IR) excess in radiation observed from stars of the B and early-A types. It is found in several groups of mostly binary systems. The recently defined FS CMa group is thought to have their gas-and-dust disks due to an earlier strong mass-transfer between the binary system components. FS CMa objects seem to possess longliving disks, whose properties have not been studied well. I will be reviewing the group properties and results of a long-term monitoring program of some of its members with a focus on detected variations of the brightness and spectrum.



Blue straggler populations beyond the Milky Way 0.5 MB
R. de Grijs, W. Sun , C. Li, L. Deng
Pages: 193-199
Abstract. Although the formation of blue straggler stars (BSSs) is routinely attributed to stellar interactions in binary systems, the relative importance of the direct collision and slow(er) stellar coalescence formation channels is still poorly understood. We selected a sample of 24 Magellanic Cloud star clusters for which multi-passband Hubble Space Telescope images are available to address this outstanding question. We compiled a BSS database, containing both traditional and evolved BSSs. We found a robust correlation between the number of BSSs in a cluster's core and its core mass, NBSS,core ∝ Mcore0.51±0.07, which supports the notion that BSS formation is linked to a population's binary fraction. At low stellar collision rates, the mass-normalised number of BSSs does not appear to depend on the collision rate, which implies that the coalescence-driven BSS formation channel dominates. Comparison with simulations suggests that stellar collisions contribute less than 20% to the total number of BSSs formed.



Kinematic and dynamic properties of young stellar cluster IC 348 0.5 MB
E. H. Nikoghosyan, H. A. Harutyunian, N. M. Azatyan, A. Grigoryan
Pages: 200-210
Abstract. In 30 - 40s of the last century Viktor Ambartsumian has published several studies on the kinematics and dynamics of stellar systems. The scientific issues of these papers not only remain relevant up to nowadays, but also are of key importance for the construction of the generalized theory of star formation. The launch of the Gaia spacecraft on December 19, 2013, opens up new horizons in the study of young stellar systems origin and evolution. The accuracy of astrometric measurements (the typical uncertainty is about 0.04 - 0.7 mas for the positions and parallaxes, and about 0.05 - 1.2 mas yr-1 for the proper motions), undoubtedly, will allow lifting the possibilities of study the kinematics and dynamics of star-forming regions to a new level. We focus our present research on the young (∼ 2 - 3Myr) stellar cluster IC 348. It has a complex structure, which includes the older compact core and the younger subgroup in the vicinity of HH 211 outflow. Based on the Gaia DR2 data, we considered the kinematic properties of both the cluster as a whole and its subgroups. We found that special velocity dispersion significantly exceeds the virial velocity dispersion and, therefore, the IC 348 stellar cluster is a supervirial or gravitationally unbound system.



Identifying birth places of high-velocity stars
V. Hambaryan
Pages: 211-222
Abstract. We searched for the high-velocity and isolated neutron stars that encountered in the past with a stellar cluster/association closer than 20 pc. We took about 830000 stars with the high-quality astrometry and radial velocities from the Gaia DR2 catalogue and empirically selected about 560 high-velocity stars.
We used a full gravitational potential of the Galaxy to calculate the motion of a stellar cluster/association and a candidate of high-velocity star from their current positions to the proximity epoch. For these calculations we used a numerical integration in rectangular, Galactocentric coordinates. We used a covariance matrices of the astrometric data for each star to estimate the accuracy of the obtained proximity distance and epoch. For this aim we used a Monte Carlo method, replaced each star with 10 000 of its simulations and studied the distribution of their individual close passages near a stellar cluster/association. In addition, we investigated a neutron star/runaway star pairs very likely both ejected from binary system during supernova event.



New Catalogue of Chemically Peculiar Stars, and Statistical Analysis 0.3 MB
S. Ghazaryan, G. Alecian, A. A. Hakobyan
Pages: 223-227
Abstract. This talk is devoted to the statistical analysis of the new catalogue of Chemically Peculiar stars compiled from papers, where chemical abundances of those stars were given. The catalogue contains chemical abundances and physical parameters of 428 stars based on high-resolution spectroscopy data. Spearman's rank correlation test was applied for 416 CP (108 HgMn, 188 ApBp and 120 AmFm) stars and the correlation between chemical abundances and different physical parameters (effective temperature, surface gravity and rotational velocity) was checked. From dozens interesting cases we secluded four cases: the Mn peculiarities in HgMn stars, the Ca correlation with respect to effective temperature in AmFm stars, the case of helium and iron in ApBp stars. We applied also Anderson-Darling (AD) test on ApBp stars to check if multiplicity is a determinant parameter for abundance peculiarities.



Investigation of the stellar content in the IRAS 05168+3634 star-forming region 0.2 MB
N. M. Azatyan, E. H. Nikoghosyan
Pages: 228-239
Abstract. We present the investigation results of structure and stellar content of a molecular cloud surrounding the five IRAS sources: 05168+3634, 05184+3635, 05177+3636, 05162+3639, and IRAS 05156+3643. Using multi-color criteria, we identified a rich population of embedded YSO candidates with infrared excess (Class 0/I and Class II) and their characteristics in a quite large molecular cloud which is located in the region of 24 arcmin radius. The molecular cloud includes 240 candidates of YSOs within the radii of sub-regions around 5 IRAS sources. The color-magnitude diagrams of the sub-regions suggest a very young stellar population. We construct the K luminosity function (KLF) of the sub-regions and according to the values of the slopes of KLFs, the age of the sub-regions can be estimated between 0.1-3 Myr. The SEDs are constructed for 45 Class I and 75 Class II evolutionary stages YSOs and the received parameters of those YSOs are well correlated with the results obtained by other methods.



Long-term photometric monitoring of FUor and FUor-like objects 0.5 MB
E. Semkov, S. Peneva, S. Ibryamov, U. Munari, H. Mito
Pages: 240-248
Abstract. A phenomenon with a significant role in stellar evolution is the FU Orionis (FUor) type of outburst. The first three (classical) FUors (FU Ori, V1515 Cyg and V1057 Cyg) are well-studied and their light curves are published in the literature. But recently, over a dozen new objects of this type were discovered, whose photometric history we do not know well. Using recent data from photometric monitoring and data from the photographic plate archives we aim to study, the long-term photometric behavior of FUor and FUor-like objects. The construction of the historical light curves of FUors could be very important for determining the beginning of the outburst, the time to reach the maximum light, the rate of increase and decrease in brightness, the pre-outburst variability of the star. So far we have published our results for the light curves of V2493 Cyg, V582 Aur, Parsamian 21 and V1647 Ori. In this paper we present new data that describe more accurate the photometric behavior of these objects. In comparing our results with light curves of the well-studied FUors (FU Ori, V1515 Cyg and V1057 Cyg), we conclude that every object shows different photometric behavior. Each known FUor has a different rate of increase and decrease in brightness and a different light curve shape.



Simultaneous photometric and spectral analysis of new outburst of V1686 Cyg 0.1 MB
H. R. Andreasyan, T. Yu. Magakian, T. A. Movsessian, M. H. Gevorgyan
Pages: 249-254
Abstract. We present an analysis of the optical observations of Herbig AeBe star V1686 Cyg, which is demonstrating photometric variability up to 3 to 4 magnitudes. We observed this star as a part of our project of young eruptive stars investigation. Observations were performed on 2.6m telescope of Byurakan Observatory. In the course of observations we noticed that this star underwent a new outburst. After data reduction we found that full rise and decline of V1686 Cyg brightness for almost 3 magnitudes lasted about 2 months. We were able to trace the changes of the stellar spectrum during the outburst. They are discussed and compared with other young eruptive variables.



Old and New Observational Data of P Cygni 0.3 MB
S. Beradze, N. Kochiashvili, R. Natsvlishvili, I. Kochiashvili, M. Vardosanidze
Pages: 255-261
Abstract. LBVs are extremely rare and enigmatic stars on the short-lived evolutionary phase with different variation scales of brightness and spectrum. Some of them are confirmed binary systems and even secondary components have found by direct imaging. The blue supergiant P Cygni is one of the prototypes of Luminous Blue Variables, showing photometric and spectroscopic variability on various timescales.
We are going to present results of the old and new photometric observations of P Cygni. Old 1951-1983 years photometric observations were made by E. Kharadze and N. Magalashvili in the Abastumani Astrophysical Observatory, Georgia, which we found, recalculated and made conclusion that the star should undergo the next great eruption in some 100 years. New observations were obtained in 2014, using the 48 cm Cassegrain telescope of the Abastumani Observatory. Some interesting behaviors of the light curves were revealed.



Revised and updated catalogue of the First Byurakan Survey of late-type stars: 2nd edition 0.3 MB
K. S. Gigoyan, A. M. Mickaelian G. R. Kostandyan
Pages: 262-267
Abstract. Eighteen lists of late-type stars (LTSs) have been published between 1990 and 2016. These LTSs have been found in the low-dispersion spectroscopic plates of the First Byurakan Survey (FBS). The systematic search and selection was carried out on a surface _16000 deg2 on almost the whole area of the FBS. As a result, \Revised And Updated Catalogue Of The First Byurakan Survey Of Late-Type Stars" was generated (LTSs, _rst version). Since 2007, all FBS low-resolution spectral plates are digitized, and Digitized First Byurakan Survey (DFBS) database and second catalog of objects has been assembled. All DFBS spectral plates are analysed with the help of standard image analysis softwares (FITSView and SAO Image ds9) and numerous of comparatively faint LTSs were discovered. We present the 2nd version of the FBS catalogue of LTSs with new data. We have made cross-correlation with the Digitized First Byurakan Survey (DFBS), the United State Naval Observatory-B1.0 Catalogue, the Two Micron All-Sky Survey (2MASS), the Wide-Field Infrared Survey Explorer (new version-ALLWISE) catalogue, the Infrared Astronomical Satellite Point Source Catalogue/Faint Source Catalogue, the AKARI catalogue, the ROSAT Bright Source Catalogue/Faint Source Catalogue, the General Catalogue of Variable Stars, Sloan Digital Sky Survey (SDSS) photometric catalogue. We have added updated IMBAD data for the objects. For numerous of the new detected objects we present accurate Digitized Sky Survey 2 positions, approximate spectral subtypes refined from the DFBS low-dispersion spectra, luminosity classes estimated from 2MASS colours, and available proper motions for 1471 FBS LTSs. 2nd Version of the Revised and Updated Catalogue lists a large number of completely new objects, which promise to extend very significantly the census of M giants, faint N-type Asymptotic Giant Branch (AGB) carbon stars, CH {type carbon giants at high Galactic latitudes, also M dwarfs in the vicinity of the Sun up to 16.0-17.0 mag. in visual. We present also some important data from the Gaia DR2 data base for FBS LTSs. Some supplementary spectra obtained with the Byurakan Observatory 2.6 m telescope and LAMOST telescope are shown.


Part II. Theoretical Astrophysics

The Growth of the Astronomical Unit and the Dark Energy Influence on the Baryonic Matter Evolution 0.1 MB
H. A. Harutyunian, A. Grigoryan
Pages: 268-278
Abstract. The effect of the Earths removal from the Sun is considered. This effect is difficult to interpret within the traditional paradigm of cosmic objects formation and evolution. Currently tidal mechanism is used as the most appropriate tool for explaining the Earth removal although no any quantitative data exist concerning the deceleration of Suns spin. We argue in favor of the dark energy influence, which, on the other hand, leads to the gradual increase of the Sun mass. Applying self-consistently all the known consequences of the interaction between the dark energy carrier and the baryonic matter, one arrives at a conclusion that the energy of the baryonic objects should grow up which, in its turn, increases their total mass. The mass growth of the Sun is estimated using the relevant observational data.



Some Problems of Solar Quiscent Prominences in the Light of Ambartsumian's Ideas 0.3 MB
A. Nikoghossian
Pages: 279-290
Abstract. The report is a brief overview of our results in the theory of spectral line formation in atmospheres with complex fine structure. The research motivation was due to interpretation of the EUV spectrum of solar quiescent prominences observed with the SUMER spectrograph as a part of the SOHO space program. We describe the methods proposed for solving the line-radiation transfer problems in multicomponent atmospheres which use Ambartsumian's ideas proposed in the theory of radiation transfer and its applications. It is demonstrated that even the simplest static model radiating medium composed of physically different types of elements shows line profiles differing from those formed in the medium with preliminarily averaged properties. The more realistic and complicated case of a multicomponent atmosphere with randomly varying properties is considered with special attention paid to the effect of the velocity field. An important role of the relative mean square deviation of observed line intensities in the diagnostics of physical features of spatial and temporal variations of prominences is shown.



Qualitative analysis of cosmological models in F(R)-gravity 0.2 MB
R. M. Avagyan, E. V. Chubaryan, G. H. Harutyunyan, A. A. Saharian
Pages: 291-302
Abstract. The spatially flat cosmological models are investigated within the framework of f(R)-gravity. An equivalent representation in the form of a scalar-tensor theory is discussed. For the general case of the f(R) function, the corresponding cosmological equations are presented in the form of a third order autonomous dynamical system. The qualitative analysis of the latter is given in the absence of nongravitational matter. Various special cases of the function F(R) are considered and the corresponding phase portraits are depicted. The possibility for the realization of a phase with accelerated expansion of the Universe is discussed.



WR galaxies and PAH: observations and modeling 0.3 MB
A. Yeghikyan, J. Martirosyan
Pages: 303-314
Abstract. This report analyzes the archival data of the Spitzer observatory for 9 WR galaxies showing PAH emission lines at 6.2 and 7.7 µ. For these galaxies, the effective radii of the emitting regions and the total number of hydrogen ionizing quanta were calculated on the base of the fluxes corrected for interstellar extinction. Using the observed values (which are obtained using SDSS data), and taking as an example stars of the WNh type (Ts = 50000 K, R = 20 R), the number of massive WR stars in the cluster and the distance to the nearest neighbor are determined. With these data, the theoretical Cloudy models, in particular, the distribution of H, and He, C, O, Ne atoms and ions along the radius are calculated. The theoretical intensities of the characteristic PAH bands at 6.2 and 7.7 µ were obtained for two types of PAH (containing 15 and 120 carbon atoms, respectively). The corpuscular radiation doses accumulated in PAH molecules due to hard irradiation by MeV protons were calculated and it was shown that such molecules had to decay for a time less than the lifetime of the cluster. A conclusion is drawn about the permanent source of PAH, most likely, the remnants of supernova explosions.



Induced cosmological constant in braneworlds with compact dimensions 0.3 MB
A. A. Saharian, H. G. Sargsyan
Pages: 315-326
Abstract. We investigate the cosmological constant induced by quantum fluctuations of a bulk charged scalar field on a brane in background of locally anti-de Sitter spacetime with toroidally compact spatial dimensions. Along compact dimension quasiperiodicity conditions are imposed with general phases and, in addition, the presence of a constant gauge field is assumed. The latter gives rise to Aharonov-Bohm type effect on the characteristics of the scalar vacuum. The renormalization of the vacuum energy density on the brane is done by making use of the generalized zeta function technique. The behavior of the cosmological constant is studied as a function of the location of the brane, of the length of the compact dimensions and of the magnetic flux enclosed by the compact dimension. In particular, it is shown that the cosmological constant is a periodic function of the magnetic flux with the period equal to the flux quantum.



Superdense stellar configurations in the Bimetric scalar-tensor theory of gravity 0.2 MB
L. Sh. Grigorian, H. F. Khachatryan, A. A. Saharian
Pages: 327-337
Abstract. We investigate static spherically symmetric configurations of gravitating masses in biometric scalar-tensor theory of gravitation. In the gravitational sector the theory contains the metric tensor, a scalar field and a background metric as an absolute variable of the theory The analysis is presented for the simplest version of the theory with a constant coupling function and a zero cosmological function. We show that, depending on the value of the theory parameter, the masses for superdense compact configurations can be essentially larger compared to the configurations in general relativity.



Electrical Resistivity and Hall Effect in Binary Neutron-Star Mergers 0.1 MB
A. Harutyunyan
Pages: 338-345
Abstract. We examine the range of rest-mass densities, temperatures and magnetic fields involved in simulations of binary neutron star mergers (BNSM) and identify the conditions under which the ideal magneto-hydrodynamics (MHD) breaks down using recently computed conductivities of warm, magnetized plasma created in such systems. While previous dissipative MHD studies of BNSM assumed that dissipation sets in due to low conduction at low rest-mass densities, we show that this paradigm must be shifted: the ideal MHD is applicable up to the regime where the hydrodynamic description of matter breaks down. We also find that the Hall effect can be important at low densities and low temperatures, where it can induce a non-dissipative rearrangement of the magnetic field. Finally, we mark the region in temperature-density plane where the hydrodynamic description breaks down.



Galaxy dynamo in inhomogeneous interstellar medium 0.3 MB
E. A. Mikhailov, D. A. Grachev
Pages: 346-352
Abstract. In some galaxies there are magnetic fields of several microgauss. Their evolution is connected with dynamo mechanism which is based on joint action of alpha-effect and differential rotation. The equations of the dynamo theory usually include some averaged kinematic characteristics of the interstellar turbulence. This approach is quite suitable for galaxies with "calm" interstellar medium. As for the galaxies with intensive star formation or supernovae explosions it will not give proper results. For this case the HII regions are quite small, exist for small-time and their localization can be assumed random. So it is useful to take the dynamo equations with random coefficients, which take one of two values (the first one is connected with HI regions, and the second one - with HII). We have studied the magnetic field evolution in the stochastic dynamo model for some typical cases. From the mathematical point of view, the results show some special effects. Firstly, the magnetic field evolution demonstrates the intermittency effect: higher statistical moments of the field grow faster than the lower ones. Moreover, the magnetic field in this model can have large fluctuations, so we have also described the correlation function of the field.



The investigation of the magnetic field inside the solar circle of the Galaxy using of pulsars with large faraday rotation values 0.2 MB
R. R. Andreasyan, H. R. Andreasyan, G. M. Paronyan
Pages: 353-363
Abstract. To study some characteristics of the interstellar medium, observational data of pulsars with large Faraday rotation values (|RM| > 300 rad / m2) were used. It was suggested and justified that large |RM|values can be due to the contribution of the regions with increased electron concentration, projected on the pulsar. Most likely these are the HII regions, dark nebulae and molecular clouds. In these objects the magnetic field can be oriented in the direction of a large-scale field of the Galaxy, or simply is a deformed extension of the galactic field. It was shown that the Galactic distribution of rotation measures of pulsars with|RM|>300 rad/m2 corresponds to the circular model of the magnetic field of the Galaxy, with the counter-clockwise direction of the magnetic field in the galactocentric circle 5 kpc < R < 7 kpc.



Analytical solution of the simple nonlinear radiative transfer problem 0.2 MB
H. V. Pikichyan
Pages: 364-372
Abstract. Exploring the "Principle of invariance" and the method of "Linear images", the simple nonlinear conservative problem of radiative transfer is analyzed. The solutions of nonlinear reection-transmission and internal field problems of one dimensional scattering-absorbing medium of finite optical thickness are obtained, whereas both boundaries of medium illuminated by powerful radiation beams. Using two different approaches - a direct and inverse problem, the analytical solution of the internal field problem is derived.



Hybrid modeling of diffusive shock acceleration in collisionless shocks in multispecies plasma 0.3 MB
J. A. Kropotina, A. M.Bykov, V. E. Ermolina, S. M. Osipov, V. I. Romansky
Pages: 373-378
Abstract. Diffusive shock acceleration (DSA) is a very efficient mechanism of high energy particle acceleration in heliosphere, supernova remnants, stellar winds and gamma-ray bursts. We present microscopic simulation of particle injection and diffusive shock acceleration which is performed with 3D divergence-conserving second-order accurate hybrid code "Maximus". Hydrogen plasma with admixture of various heavy ions is considered. The injection process is found to start through shock reflection for both hydrogen and heavier ions. However, the reflection process depends on charge-to-mass ratio. While hydrogen ions reflection appears at shock ramp and is governed by the cross-shock potential, the reflection of ions with greater A=Z proceeds deeper down-stream via gyration in perpendicular magnetic field component. The heavy ions appear to inject into the DSA preferentially, but this chemical enhancement saturates with growing A=Z. The protons injection efficiency is estimated within various approaches, and it is shown that about 20% of initial flow energy goes into accelerated particles.


Part III. Extragalactic Astronomy

The impact of spiral density waves on star formation distribution: a view from core-collapse supernovae 0.2 MB
A. G. Karapetyan, A. A. Hakobyan, L. V. Barkhudaryan, G. A. Mamon, D. Kunth, V. Adibekyan, M. Turatto
Pages: 379-384
Abstract. We present an analysis of the impact of spiral density waves (DWs) on the radial and surface density distributions of core-collapse (CC) supernovae (SNe) in host galaxies with different arm classes. For the first time, we show that the corotation radius normalized surface density distribution of CC SNe (tracers of massive star formation) indicates a dip at corotation in long-armed grand-design (LGD) galaxies. The high SNe surface density just inside and outside corotation may be the sign of triggered massive star formation by the DWs. Our results may support the large-scale shock scenario induced by spiral DWs in LGD galaxies, which predicts a higher star formation efficiency around the shock fronts, avoiding the corotation region.



Number count of 2MRS galaxies in the J, H, K bands 0.2 MB
S. Arbabi Bidgoli, M. Rah, A. Youse_Sostani
Pages: 385-391
Abstract. The Copernican principle has been the motivation for the present study on the number density of galaxies. In this work we have carried out a number count of galaxies in the 2MRS catalog in the K, H and J bands. The results presented here have obtained on volume-limited samples with equal widths or redshift bins. The main result of this study is the number count of galaxies which have been plotted in concentric spherical shells with the observer at the center. The obtained result in the three bands show a similar behavior up to a distance of 1.7 × 102 Mpc and behave differently from there on.



Abundance and Star Formation Determinations in Mrk galaxies from SDSS Spectra 0.2 MB
M. V. Gyulzadyan, A. M. Mickaelian, H. H. Abrahamyan, G. A. Mikayelyan, G. M. Paronyan
Pages: 392-397
Abstract. We analyse the oxygen and nitrogen abundance and specific star formation rates (sSFR) in Markarian galaxies from Sloan Digital Sky Survey (SDSS) spectra. The Data Release 7 (DR7) of SDSS contains photometric data for more there 1000 and spectral information for more than 700 Markarian objects. The Mrk sample has played a central role in the task of distinguishing between the astrophysical different types of phenomena that occur in AGNs. In the course of the Markarian survey, more than 200 Seyfert galaxies, and hundreds of starburst, blue compact, and H II galaxies were discovered. The Markarian survey remains perhaps the best-known source of such objects in the local universe. We have measured their line fluxes and derived the O and N abundances using recent calibrations. We have compared the oxygen and nitrogen abundances derived from global emission-line Sloan Digital Sky Survey (SDSS) spectra of galaxies using (1) the Te method and (2) two recent strong-line calibrations: the ON and NS calibrations. The behaviour of the [N/H] ratio in under abundant regions gives strong support to a partially primary origin of nitrogen. The star formation rate (SFR) is one of the main parameters used to analyse the evolution of galaxies through time. In the local Universe, the Hα luminosity derived from IFS observations can be used to measure SFR, at least in statistically significant, optically-selected galaxy samples, once stellar continuum absorption and dust attenuation effects are accounted for.



The investigations of extended radio galaxy NGC6251 and the galaxies in the environment 0.05 MB
M. A. Hovhannisyan, R. R. Andreasyan, G. M. Paronyan
Pages: 398-400
Abstract. The environment of one of the most extended radio galaxies, NGC 6251, has been studied. The surface density of the environment galaxies in the region with the radius 300 arcmin around a radio galaxy NGC 6251 is 0.0315 in one arcmin2. In the distances less than 180 arcmin, the density of galaxies decreases, which is most likely due to the strong radio loudness and the interaction of radio galaxy with its surroundings.



Dependencies between the magnitude gap of groups and the morphology of two brightest galaxies 0.05 MB
A. P. Mahtessian, V. H. Movsisyan, L. A. Mahtessian, G. S. Karapetian
Pages: 401-406
Abstract. In the present study, the dependencies of the morphological types of the first and second ranked group galaxies on the magnitude gap were studied.
It is shown that there is no increase in the relative number of elliptical galaxies among the first and second ranked group galaxies with large magnitude gaps (in comparison with the expectation, by assuming that the morphological type of these galaxies does not depend on the magnitude gap). This result contradicts the merger hypothesis. The hypothesis proposed by Ambartsumian does not contradict this result.



Searches of Galaxies Clusters Around Radio Galaxies with Different Linear Sizes 0.05 MB
G. A. Ohanyan
Pages: 407-411
Abstract. In order to understand how galaxies have formed and evolved in dense environments, and how these environments themselves evolve, we use the method of optical photometric survey of the field around radio galaxies. For this purpose, a statistical significant sample of radio galaxies consisting of 3 size radio source subclasses - GPS, CSS and FRI/II is selected for observations at the 1m Schmidt telescope of the Byurakan Astrophysical Observatory. This method will allow us not only to detect distant clusters of galaxies, but also watch the sequence of development of these clusters - how changes their compactness, richness, and so on.



Activity types of galaxies selected from HRC/BHRC sample 0.05 MB
G. M. Paronyan, A. M. Mickaelian, H. V. Abrahamyan, G. A. Mikayelyan
Pages: 412-416
Abstract. In this study we carry out detailed spectral classification of 123 AGN candidates from the Joint HRC/BHRC sample, which is a combination of HRC (Hamburg-ROSAT Catalogue) and BHRC (Byurakan-Hamburg-ROSAT Catalogue). These objects were revealed as optical counterparts for ROSAT X-ray sources, however spectra for 123 of them are given in SDSS-III, IV without definite spectral classification. We studied these 123 objects using the SDSS spectra and revealed the detailed activity types for them. Three diagnostic diagrams and direct examination of the spectra were used to have more confident classification. We also made identification of these sources in other wavelength ranges and calculated some of their parameters.



On the Connection between Galaxies with Ultraviolet Excess 0.1 MB
A. A. Yeghiazaryan
Pages: 417-420
Abstract. A possible correlation between the characteristic parameters of physically coupled galaxies with ultraviolet excess is discussed. It is known that for mutually independent combinations the observed number of galactic pairs with Markarian components is greater than expected. It is shown, that the most of nearby Kazarian galaxies with ultraviolet excess form physical systems.