Marat ARAKELIAN (1929-1983)
Prof. Arakelian is one of the prominent Byurakan astronomers, the author of famous Arakelian galaxies, which at present are target for many-sided studies with ground-based and space telescopes. Arakelian is known as a distinguished specialist in the theoretical astrophysics and extragalactic astronomy.
Marat Arsen Arakelian was born on January 15, 1929, in Goris, Armenia, USSR. He studied at the Physical-Mathematical Department of the Yerevan State University (YSU) and graduated from it in 1951, among the first students specialized on Astrophysics. He was directed to the Byurakan Astrophysical Observatory (BAO), where he worked first as assistant astronomer, and later as junior research associate. Soon he became a postgraduate student at the Leningrad State University (LSU, presently, St. Petersburg), finished the studies in 1955, and in 1956 successfully passed his Ph.D. thesis "Spectrophotometric investigation of Algol" under the supervision of Prof. O.A. Melnikov at the LSU.
In 1957-1959 Arakelian combines his work with senior teacher position at the Department of Astrophysics of the YSU. From 1960 to 1966 he was a junior researcher and lectured at the LSU. He was awarded the title of Associate Professor. Later on, since 1966 Arakelian again works at BAO and combines his research with a position of a lecturer at the Department of Astrophysics of the YSU. In 1967, he became a senior researcher at BAO and headed an important direction in the extragalactic astronomy.
Since 1967, Arakelian completely devoted himself to the research work and during a short period performed a fantastic productivity for those times, publishing 62 papers in 1968-1983, and giving important scientific results in almost each of these works! Let us give the list of his results and achievements:
1968, Study of the luminosity function and the stellar space density in the solar neighbourhood. The results were published in Astrophysics.
1968-1969, Study of the luminosity evolution of quasars based on the evolutionary effects associated with them. The results were published in Astrophysics (Астрофизика, 2 papers in 1969-1970), in Soviet Astronomical Circular (Астрономический циркуляр), and a summary of these works was published in the prestigious journal Nature in 1970 (vol. 225, p. 358-359).
1969-1970, Statistical study of flare stars in the solar vicinity. The results were published in Commumications of the Konkoly Observatory, Communications of BAO, and were reported at the conference “Non-periodic phenomena in variable stars” in 1969.
1970, Derivation of the luminosity function of field galaxies (together with A.T. Kalloghlian). The results were published in Soviet Astronomy (Астрономический журнал).
1970-1971, The proof of the extragalactic origin of quasars. The results were published in Astrophysics and Вестник АН СССР (Bulletin of the USSR Acad. Sci.).
1970-1973, Spectroscopic observations and studies of a few hundred Markarian galaxies and discovery of more than 40 new Seyferts among them (together with Russian astronomers E.A. Dibai and V.F. Esipov). The results were published in series of 8 papers in Astrophysics and 5 papers in the Soviet Astronomical Circular.
1972-1974, Analysis of the surface brightness of emission-line galaxies (including Seyfert and Markarian ones) and development of method for revealing galaxies with high surface brightness. The results were published in 3 papers in Astrophysics.
1973, Suggestion of a new method for definition of space density of extragalactic objects and estimation of the mean density of matter in the Metagalaxy. The results were published in Astrophysics.
1975, Compilation and publication of the catalogue of “Galaxies of high surface brightness” (named Arakelian galaxies, Akn), a list of 621 objects with surface brightness at least 22.0 magnitudes from an area of 1 sq. arcsec. The sample contained 4% of all galaxies in an area of with d>-3° and |b|>20°. Arakelian catalog became a source for many new AGN (Communications of BAO, No. 47, p. 3-42, 1975).
1975, Derivations of the luminosity function and space density of galaxies with UV continuum (Markarian galaxies). The results were published in Soviet Astronomy.
1975-1976, Spectroscopic observations and studies of Arakelian galaxies (galaxies with high surface brightness) and discovery of new Seyferts among them (together with E.A. Dibai and V.F. Esipov). The results were published in a series of 4 papers in Astrophysics, a paper in the Soviet Astronomical Circular, and were reported in the meeting “Stars and galaxies from observational points of view” in 1975.
1976-1977, Study of the dependence of the emission-line intensities of Markarian and Seyfert galaxies on their color index. The results were published in 2 papers in Astrophysics.
1977, Study of the distribution of the mean surface brightness of galaxies in the Coma cluster. The results were published in Astrophysics.
1977-1980, Study of the relation between the mean surface brightness and radio emission of galaxies, including Seyfert galaxies (together with R.A. Kandalyan). The results were published in 2 papers in Astrophysics.
1981, Study of the estimations of the kinetic energies of clusters of galaxies; the extent to which a kinetic energy estimate would be affected by a possible mass dependence of the velocity dispersion of galaxies in clusters was considered. It was concluded that in some cases the kinetic energy might be underestimated (together with A.G. Kritsuk). The results were published in Astrophysics.
1980-1981, Radio (6cm) observations of Arakelian galaxies and publication of their accurate positions (together with US astronomers G. Kojoian, D.F. Dickinson, R. Elliott, M.D. Bicay). The results were published in the Astronomical Journal.
1981-1982, Comparative study and statistics of the surface brightness and morphological types of isolated and double galaxies (together with A.P. Mahtessian). The results were published in 2 papers in Astrophysics.
1981-1982, Study of Seyfert galaxies in clusters and Seyfert properties of the cluster galaxies (together with V.Yu. Terebizh). The results were published in the Soviet Astronomical Circular and Soviet Astronomy Letters (Письма в Астрономический журнал).
1983, Proposing a method for construction of the luminosity function of the components of double galaxies on the basis of an arbitrary sample of pairs of galaxies. The results were applied to the data of Karachentsev's Catalog of Isolated Pairs. The presence of a correlation between the absolute magnitudes of the components of pairs was confirmed. The results were published in Astrophysics.
1986, A method for the determination of the bivariate luminosity function utilizing an incomplete sample with an application to Seyfert galaxies. It was shown that the results of incomplete radio and X-ray surveys could be used for the determination of the bivariate luminosity functions, having both the distribution of luminosities of objects in the detected subsample and the distribution of apparent magnitudes in the surveyed sample. A paper was published in Astrophysical Journal after Arakelian’s death.
Summarizing, Arakelian has compiled and published the catalog of 621 high-surface-brightness galaxies, has proved the extragalactic origin of quasars, has determined the space density of extragalactic objects, has proposed several methods for study of properties of extragalactic objects, has made a comparative analysis of properties of different types of galaxies, and with his Russian colleagues spectroscopically has observed and studied some 800 faint galaxies and quasars. Arakelian galaxies have been observed in many observatories in the USA, UK, USSR, and elsewhere in optical wavelengths, radio and X-rays. Especially interesting objects are Akn 120 and Akn 564 (both are strongly variable AGN in X-ray and optical wavelengths; Akn 564 is a Narrow-Line Seyfert 1 galaxy that strongly changes the intensities of its emission lines).
In 1977, Arakelian defended his second Doctoral Degree thesis "Spectral observations and statistics of galaxies with active nuclei" at the Moscow State University (MSU) and became a Doctor of Sciences.
Arakelian combined his scientific work with pedagogical one as well. In 1982 he was elected the Chair of the Department of Astrophysics and Theoretical Physics of the Armenian State Pedagogical Institute after Kh. Abovian. Together with L.V. Mirzoyan, A.T. Kalloghlian, and H.M. Tovmassian, he was the co-author of the textbook “Astronomy” for secondary schools (three editions in 1970, 1971, and 1973). Arakelian has written an extended review on Clusters of galaxies in the book “Problems of extragalactic astronomy” (1981).
Arakelian has published about 80 papers in various astrophysical journals, including such prestigious journals, as Nature, Astronomical Journal, and Astrophysical Journal (one of the rare Byurakan astronomers to publish a paper in Nature), as well as in proceedings of several international conferences. He was the editor of the two proceedings books of the Byurakan meetings: “The Non-Stable Stars” (1956) and the IAU Symp. #29 “Non-Stable Phenomena in Galaxies” (1966).
Since 1973, Arakelian was a member of the International Astronomical Union (IAU), Commission #28 “Galaxies”.
M.A. Arakelian passed away very early, at the age of 54 years on January 20, 1983, in Moscow, when he was at the period of prosperity of his scientific activity.