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Marat ARAKELIAN (1929-1983) |
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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.