Beniamin Egishevich Markarian is one of the most well-known astronomers in the field of classification of Active Galactic Nuclei. From photometric study of a number of galaxies in 1958-1962 and comparison of their spectra, Markarian concluded that colors of the central parts of many galaxies do not correspond to their morphological type, i.e. they were bluer than for normal galaxies of the same morphological type. In 1963 he published a list of 41 such objects, including 8 Seyfert galaxies with broad emission lines. He proposed a non-thermal origin of the emission from such nuclei. Markarian devised a quite new technique for searching active galaxies by analysing an ultra-violet excess in their emission. He was the first who proposed to use the low-dispersion prism (1800 A/mm at the H-gamma region) with the 40'' Schmidt telescope of the Byurakan Astrophysical Observatory to obtain spectra of such nuclei. High spectral resolution was not necessary for their spectral classification, therefore the limiting magnitude of the photographically detected objects corresponded to 17-17.5 magnitude. In 1965-1966 Markarian detected 70 new galaxies with UV continuum named later as Markarian galaxies.
The first slit spectra were obtained in USA by Weedman and Khachikian (1968, 1969), and led to the detection of 8 new SyG. It should be noted that at that time only 10 SyG, detected by Seyfert in 1943, were known. So, the new technique for searching AGNs turned out to be highly effective. In 1969 Markarian published 2 more lists of such galaxies. Because of the health Beniamin Egishevich at that time could not continue the telescope observations. He decided to invite a young researcher Valentin Lipovetskij from the Kiev University Observatory, Ukraine, to perform the observations and the preliminary study of photographic plates. They worked in close contact and with a full mutual understanding. Both were fanatically enthusiastic about this work.
In 1969 Markarian together with Lipovetskij began a survey of all the Northern Sky named later as the First Byurakan Survey. The goal of the survey was the study of galaxies with UV continuum and their spectral classification. This was really a gigantic work! During the nights V.A.Lipovestkij performed observations, and at the daytime he was looking through the photographic plates to select interesting objects. The marked objects were carefully analyzed together with B.E.Markarian. After many discussions the lists of Markarian galaxies were compiled. The observations with the objective prism at the 40'' Schmidt telescope were finished in 1978, and the review of all plates and search for objects – in 1980. More than 2500 photographic plates were obtained. About 40,000,000 images were reviewed visually. The survey consists of 1133 fields (4x4 degrees) and covers the sky area of about 17,000 square degrees. Basic results were published in the series of 15 papers (1967-1981) comprising 1500 objects. The first three lists were published by Markarian, lists 4-9 - by Markarian and Lipovetskij, lists 10-15 - by Markarian, Lipovetskij and Stepanian.
Since 1969 the authors began regular spectroscopic observations of these galaxies. Before 1977 the spectra of Markarian galaxies were recorded photographically using mainly three telescopes: the 1.25 m at the Southern Station of the Sternberg Astronomical Institute in Crimea, the 2.6 m of the Crimean Astrophysical Observatory and the 70 cm telescope of the Astrophysical Institute in Alma-Ata.
After 1977 most of the spectra were obtained with the 6 m BTA telescope of the Special Astrophysical Observatory (SAO). The observations at the 6 m telescope were carried out by V.A.Lipovetskij, V.L.Afanasiev, A.I.Shapovalova (SAO), J.A.Stepanian and L.K.Erastova (BAO). In 1978-1984 the photographic spectra were scanned in SAO using the automatic scanning microphotometer "Spectrum-Code", and then they were processed with the IBM M-200 by using the software developed by A.L.Scherbanovskij. Since 1985 the spectra were recorded using the television scanner of the 6-m telescope. Till 1985 the analysis of the processed spectra was made in the close contact with B.E.Markarian.
All in all, the slit spectra of about 1200 objects were obtained, more than 600 of them being obtained with the BTA. Part of objects, that was obtained earlier with other telescopes, was re-observed once more with the 6 m telescope, since the quality of spectrogramms from smaller instruments did not allow to determine the redshift and to classify the objects. The result of this giant work is a catalogue of Markarian galaxies (Markarian B.E., Lipovetskij V.A., Stepanian J.A., Erastova L.K., Shapovalova A.I., Soobscheniya SAO, 62, 1989) published already after the death of B.E.Markarian. The catalogue contains 1512 objects. Among them there are about 200 SyG, 13 QSO, 903 emission galaxies. In his PhD dissertation V.A.Lipovetskij made the detailed description of the FBS and presented some statistical results of the study fulfilled on the basis of the catalogue, with account for the survey completeness, the luminosity function, the spatial distribution, etc. It should be noted that the program of classification of AGN by slit spectra was one of the first priority programs at the 6-m telescope during more than 20 years. It received a lot of observing time, and the analysis was successfully fulfilled jointly by the researcher from SAO and BAO, first under the direction of B.E.Markarian, then under the direction of V.A.Lipovetskij. The study of AGN both in classification and in detection of new objects and numerous detailed investigations of selected interesting AGNs is one of basic topics of SAO during almost 30 years.
The Second Byurakan Survey (SBS) is a continuation of the FBS. It was started in the Byurakan Observatory by Markarian, Lipovetskij and Stepanian after 1980. The SBS observations were performed in the selected regions of the Northern sky, covering about 1000 sq.degrees, between 8h and 17h in right ascension and +49 deg. and +61 deg. in declination. The objects up to 19.5 magn. were selected visually. Before 1985 the review of the plates and the preparation of the lists was made by Markarian, Stepanian, Lipovetskij and Erastova, after 1985 mainly by Stepanian and Erastova with the participation of Lipovetskij. The lists of SBS contain several thousands objects. 1500 stellar-like objects were selected among them. The slit spectra were obtained with the 6-m telescope by Lipovetskij, Stepanian, Shapovalova, Erastova, and Chavushan. In 1990-1991 five lists of new objects were published. More than 600 quasars and more than hundred blue compact dwarf galaxies were detected among them. The results of the SBS classification were analysed in details in the doctorate thesis of Stepanian (1995).
Thus, a successful use of objective prism for the study of faint objects gave impetus to a new direction of extragalactic astronomy – systematic search for new objects by means of low-dispersion spectroscopy. This technique was thereafter used in all surveys all over the world: Cerro-Tololo Survey, Michigan Survey, Case Survey, etc. The continuation of the survey, proposed by Markarian, led to the mass detection of AGNs. Though B.E.Markarian and his talented pupil V.A.Lipovetskij are not with us any more, the study of Markarian galaxies in different spectral ranges is continued by many researchers all over the world.
Dr. Yuri Yu. BALEGA
Director, Special Astrophysical Observatory (SAO), Russia
Dr. Alla I. SHAPOVALOVA
Senior researcher, Special Astrophysical Observatory (SAO), Russia