29-30 August 2005,
The Fourth Annual Meeting of the Armenian Astronomical Society was held on August 29-30, 2005, in Byurakan. It was organized jointly by the Armenian Astronomical Society and the Byurakan Astrophysical Observatory.
Some 40 astronomers participated in the Meeting, including scientists from Germany (T.Arshakian, V.Hambaryan, T.Khanzadyan), Yerevan State University (YSU), and some 35 scientists from the Byurakan Observatory, as well as 14 YSU students attending the Summer School which was attached to the ArAS meeting (see "Second Byurakan Summer School").
was opened with a welcome address by Haik Harutyunian,
ArAS Co-President, followed by a report by Areg
Mickaelian, another ArAS Co-President, who presented the
was sponsored by Mr. David Nelson (
(brief texts for some of the contributions)
The 3D structure of the magnetic field of the Galaxy
The activity of cosmic objects is associated in most cases with the presence of magnetic fields of different scales, natures and strength. The large-scale magnetic field in our Galaxy was found in 1950-th, and till now is studied hardly using all available methods (Parker 1979), based on the analyses of optical and radio polarization data and measurements of Rotation Measure (RM) of extragalactic radio sources and pulsars etc. It seems to be very important to take into account of magnetic field distribution in galaxies, and partially in our Galaxy, when we study the formation and evolution of galactic structural features as well as a whole morphology of optical and radio galaxies and quasars. Many attempts have been made to find the distribution of the large-scale magnetic field of our Galaxy. It was shown that three classes of model are viable for the large-scale structure of magnetic field in the disk of Galaxy: 1. a bisymmetric spiral (BSS), in which the field direction reverses from arm to arm (Simard-Normandin & Kronberg 1980; Sofue & Fujimoto 1983, Andreasyan & Makarov 1989, Han et.al., 2002); 2. an axisiymmetric spiral (ASS), with two field reversals inside the Solar Circle, Vallee (1991,1996), Poezd et al.,(1993); 3. a concentric ring model, Rand & Kulkarni (1989), Rand & Lyne (1994).
In the recent study by Indrani & Despande (1998) a model was suggested involving a magnetic field with the spiral structure lying in the inter arm regions. Studies of polarized radio emission from spiral galaxies (Beck et. al.1996) show galactic-scale magnetic fields, with a pitch angle similar to that, of the spiral arm. Observations by Beck & Hoernes (1996) show that in the galaxy NGC 6946 also the magnetic spiral structure lies in the inter-arm region.
Halo magnetic fields also were observed in many galaxies. The Halo magnetic fields may be: 1. Poloidal, as in NGC 4631 (Hummel, Beck & Dahlem 1991); 2. May be parallel to the galactic disk, as in NGC 253 (Beck et. al.1994); 3. Show a filamentary structure, as in NGC 4666 (Dahlem et al.1997). The Halo magnetic field of our Galaxy was studied by Andreasyan & Makarov (1988, 1989). It was suggested that the distribution of RMs of pulsars and extragalactic radio sources are consistent with a Halo magnetic field of opposite sign above and below the Galactic plane. . Han et al. (1997) (1999) obtained a similar result for the Halo magnetic field of the Galaxy, and estimated the vertical component of magnetic field to be B=0.37 ?G, directed toward the North Galactic pole. These results are in agreement with the dipole magnetic field model for the Halo, but deformed by the differential rotation of the Galaxy, as proposed by Andreasyan & Makarov (1988, 1989).
So, in spite of a large number of papers studying the structure of galactic magnetic field, there is no generally accepted model.
Here we study the 3-dimensional distribution of Galactic magnetic field, using all available rotation measure data of pulsars. Since the time of our earlier studies, much more data has become available for this investigation, particularly for more distant pulsars (e.g. Rand & Lyne 1994; Han et al. 1997). The total number of pulsars with known values of the rotation measure -RM, now is 363. We use this improved database for the study of 3-dimentional model for whole galactic magnetic field. We divide the study on two part; 1. The study of the magnetic field in the region near to galactic plane (plane component) with |z|<z_o pc, where z – is the distance from the galactic plane, and the value of half thickness of plane component zo can be changed in different versions of calculation; 2. The second stage is the study of Halo component of magnetic field with |z|>z_o pc.
It is well known that pulsars are strongly concentrated to the galactic plane, and there are not so many pulsars in the Halo region. Therefore we use different methods for the study of magnetic fields of Plane component and Halo component. For the Plane component, using data of much more pulsars, we construct the map of distribution of magnetic field in the galactic plane. It is known that for pulsars
RM = \alpha^RxInt(n_eB_LdL), (\alpha=8.1.10^5) (1)
DM = RxIntn_edL, (2)
where DM – is the dispersion measure of pulsar, which is known practically for all pulsars from the observations, BL is the component of the magnetic field along the line of sight (in G), R- the distance of pulsar from the Sun, ne is the electron density (cm-3), and the integral is taken over a distance L (pc). Equation (1) and (2) yield
<B_L> = (1/\alpha)d(RM)/d(DM), (3)
B_L(DM) = (1/\alpha)d(RM)/d(DM) (4)
B_L(R)n_e(R) = (1/\alpha)d(RM)/d(R) (5)
Here ‹BL› is the magnetic field strength averaged along the line of sight, and BL(DM) is the line of sight component of magnetic field strength at the point with a given value of DM (unlike to averaged value of ‹BL›), BL(R) is the line of sight component of magnetic field strength at the point with a distance R from the Sun. It means, that using the RM-DM and RM-R dependences for a given direction, it is possible to find BL(DM) for each value of DM, and BL(R)ne(R) for each value of R. We can find the RM-DM dependence for all directions in the plan of Galaxy using averaging procedure similar to one presented in Andreasyan et.al (2005). That is, we use the method, when the coordinates (l;DM) of the center of averaging region (where - l is the galactic longitude, DM – the dispersion measure), with the constant number of pulsars, is changing smoothly in the plane of (l;DM). So we find the dependence of average values of RM from the average value of DM in every direction, and from the formula (4) find the BL(DM). This is true also for the RM-R dependence, and from the formula (5) we find the BL(R)ne(R). In fact we are solving the inverse problem to construct 2-dimensional model for plane component of Galactic magnetic field with coordinates (l;DM), or (l;R).
Some of the results of calculations are given on the maps of BL(R)ne(R) and BL(DM) (fig1 and fig.2), which are constructed for some restrictions on the z coordinate. In the fig.1 we have the distribution of BL(R)ne(R) in the galactic plane (l;R). The Sun is located in the center of the distribution. The galactic longitude l increases opposite to the clockwise, and the center of the galaxy is directed to the right (green point). The distance of the sun from the center of Galaxy is accepted 8.5 kpc. On the maps pulsars are marked by circles of different color. The blue color of circles and averaging regions indicates that the magnetic field component is directed to the observer (RM>0), and the red color we use for the magnetic field component directed from the observer (RM<0). As dense is the color, as large is the value of BL(R)ne(R). On the picture we have the distribution of BL(R)ne(R): for all pulsars with known RM (-1800<z<1800pc); for the plane component of magnetic field (-400 <z<400pc, -400<z<0pc and (-0<z<400pc); and the distribution for the Halo region -1800<z<-400pc and 400<z<1800pc. The restriction ?z?<1800pc for Halo region comes from the catalogues of pulsars. On the map with -400 <z<400pc we see the reversals of magnetic field directions from one spiral arm to another, what is consistent with the results of previous studies (for example, see Han et al. 2002). But in the maps with -400<z<0pc and -0<z<400pc we see large differences. The main difference in the pictures for South and North hemispheres is the magnetic field distribution in the direction of Sagittarius spiral arm (l ? 55o). The very strong and homogeneous magnetic field of Sagittarius spiral arm, directed to the observer (blue color), appears only in the North hemispheres. This distribution is consistent with the results of Andreasian et al (2003). There are also other large scale features on the fig.1, the detail investigation of which is in progress.
The study of the magnetic field of Halo region (in fig.1 regions -1800<z<-400pc and 400<z<1800pc.), using relatively less observational data, is also in progress, and gives preliminary results, that are consistent with the results of Andreasyan & Makarov (1988,1989) and Han et al. (1997,1999).
We must note that the results, obtained from the fig.1 for Plane component of Galactic magnetic field depends strongly from the method of estimation of pulsars distances. It is obvious, that these results reflect the spiral arm model of electron density distribution (Taylor & Cordes, 1993), used for the estimation of pulsar distances. It is the reason, that for the detail investigation we use also the distribution of BL(DM). We bring here, for example, one of these distributions (fig.2). In this picture, as one of coordinates, we use the averaged dispersion measure instead of averaged distance from the Sun. The galactic longitude increases opposite to clockwise (the center of the galaxy is directed to the right). From the picture we see, that the maps for pulsars with -20<K<20 (K=DM.Sinb pc.cm-3, b is the galactic latitude), and for pulsars with -20<K<0 and 0<K<20 are different. The main difference in the pictures for South and North hemispheres, as in the picture 1, is the magnetic field distribution in the direction of Sagittarius spiral arm. Magnetic field of Sagittarius spiral arm appears only in the North hemisphere.
From the distribution of BL(DM) we can find the distribution of BL(R), using the new distribution (DM)L-R (see Andreasyan et al. 2005, and Andreasyan 2004, “The Progress Repor of ANSEF Grant No. 04-ps-astroph-812-73 “THE DISTRIBUTION OF FREE ELECTRONS IN THE GALAXY”;). The investigation of all these problems is in progress.
L I T E R A T U R E
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Andreasyan, R.R., Balayan, S. & Mavsisyan, V. 2005, “The distribution of free electrons in the Galaxy'' Astrophysics, in preparation.
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1979, Cosmical magnetic fields, their origin and
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Rand, R.J. & Lyne, A.G., 1994, MNRAS, 268, 497.
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Sofue, Y. & Fujimoto, M., 1983, ApJ, 265, 722.
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3C 390.3 radio galaxy:
the link between the compact jet and the variable optical continuum
Max-Planck-Institut fur Radioastronomie (MPIfR),
The "central engine" of AGN is thought to be powered by accretion on a central nucleus believed to be a super-massive black hole. The localization and exact mechanism of the energy release in AGN are still not well understood. We present observational evidence for the link between variability of the radio emission of the compact jet, optical and X-ray continua emission and ejections of new jet components in the radio galaxy 3C 390.3. The time delays between the light curves of the individual jet components and the light curve of the optical continuum are estimated by using minimization methods and the discrete correlation function. We find that the variations of the optical continuum are correlated with radio emission from a stationary feature in the jet. This correlation indicates that the source of variable non-thermal continuum radiation is located in the innermost part of the relativistic jet at a distance ~0.4 parsecs from the central engine. We suggest that the continuum emission from the jet and counterjet ionizes material in a subrelativistic outflow surrounding the jet, which results in a formation of two conical regions with broad emission lines (in addition to the conventional broad line region around the central nucleus).
The large distance of the continuum source from the central engine challenges the existing models in which the broad-line emission is localized exclusively around the disk or near the central engine. It also questions the assumption of virialized motion in the BLR in radio-loud AGN, which forms the foundation of the method for estimating black hole masses from reverberation mapping.
Active dwarf galaxies as
circumnuclear regions of LSB-galaxies
It is shown that in their structure, morphology, sizes, and luminosities, the active dwarf galaxies reveal a tight similarity to the nuclear regions of normal in size galaxies with active nuclei. There are a number of examples, when a dwarf galaxy turn out to be an active nuclear region of an extended LSB-galaxy if observed in deep images. On the basis of the abovementioned, an assumption is made that active dwarf galaxies or some of their parts are isolated naked nuclear regions of the LSB-galaxies having extended halos, which may not be observed at present even with the largest telescopes. It may turn out that all or most of the active dwarf galaxies are giant spiral galaxies with peripheries or LSB-type host galaxies.
Cosmic expansion and phenomenon of activity
Study of MgII 2800 h and k line profiles
obtained with IUE in A-type stars
Once more about Astroparticle
Byurakan Astrophysical Observatory (BAO), Byurakan
During 1993-2000 years author has presented some short contributions to different International workshops. There are observational facts in these contributions, speaking in favour of the unity of micro and macro worlds of the Universe: fact of the existence of closed looplike superstring in Our Supergalaxy (1), fact that M87 is the active nucleus of Our Supergalaxy (2), that M87 with its immediate environment is also the nearest "void" (3), observational facts about existence of similar structures-similar formations of large and small scales and later, fact also about similar phenomena of large and small scales in the Universe (4,5), discovery of the observational facts about similar behaviour of galaxies and elementary particles (6), when last ones are in conditions of the beginning moment of the Big-Bang, when high energies released at high temperatures, discovery of the fundamental basis of author's idea about subordinating of micro and macro worlds of the Universe to the same general regularity, in which, may be, is hidden the most beautiful symmetry in the Universe (it is ejection of the first type stellar population from the entrails of the second type one (in protogalactic stage, of course) (it is betta decay in micro world).
All these above mentioned observational facts,author's scientific thoughts and ideas (7,8), author's new approaches to some aspects of extragalactic astrophysics (9,10), all of these were presented to different international workshops and helped to rise the new branch of science, which was called by physicists-theoreticians very nice name "astroparticle".
It was found also a very interesting from the sight of view of the new science observational fact. One can see physical connection between groups N94 and N106 obviously from (11) (look at Fig. 1a,b,c (2)). The brightest members of N94 group show distribution, liking to closed looplike superstring (fig.1c). There is a similar connection between NGC4038-39 and NGC4027 in more small scale. Interesting fact is about the similar populations of both loops-the loop of superstring and the loop of NGC4038-39. Both contain only very late type population. The loop of superstring consists from late type galaxies (Fig.1c), the loop of NGC4038-39 consists of superassociations only. Such a similarity cannot be by chance. Sooner it is a result of the same way of origin of the loops and strings, but on different scales.
There has been made three contributions already about astroparticle (12-14) by author, that's why the last one has been called "Once more about astroparticle".
R e f e r e n c e s
"An Example of Closed Looplike
Superstring". Euroconference "The Evolution
of Galaxies on Cosmological Timescales", 30th November-5th December 1998,
Puerto de la Cruz,
"Is M87 the Active Nucleus of Our Supergalaxy?".
International workshop on "Galaxy Clusters and Large Scale Structures in
the Universe", Sesto Pusteria (
"The Nearest "Void?"", International workshop on
"Observational Cosmology: from Galaxies to Galaxy Systems" Sesto Pusteria (
"Similar Structures-Similar Formations of Large and Small Scales",International workshop on"Observational
Cosmology:from Galaxies to Galaxy Systems",Sesto
"Is SN Phenomenon Micro Scale Form of the Big-Bang", International
workshop on"The Largest Explosions Since the
Big-Bang:Supernovae and Gamma Ray Bursts",hosted
"Similar Behaviour of Galaxies and Elementary Paricles" International workshop on"Hubble
Deep Fields", 9-12 October, 2000,
Unity of the Universe",International workshop on
"Hubble Deep Fields",6-9 May,1996,
"The Universe of Micro and Macro Scales", Astro
Meeting-4, 24-29 November, 1997,
"New Approaches in Astrophysics", JENAM-2000, May 29th
10.S.G.Iskudarian,"New Approaches in Astropysics",
Nomination for the Cosmology Prize of the Peter Gruber Foundation, March 2 -
11.M.J.Geller,J.P.Huchra, Astrophys.J.,Suppl.Ser., 52, 61, 1983.
is My Baby", Carolina Hershell Visitor Programme for Enhance Women,
is My Baby", VAC-4,
14.S.G.Iskudarian, "How was born Astroparticle
- New Branch of Science", International workshop on"Very
High Energy Phenomena in the
Universe", Moriond, 12-19 March, 2005,
Imprints of Star-Formation
Max-Planck-Institut fur Astronomie (MPIA), Heidelberg, Germany
Jets in the HL/XZ Tau region
The Astrophysical Virtual Observatories (VOs) have been created for construction of a modern system for data archiving, extraction, acquisition, reduction, use and publication, and for establishment a new environment for modern research based on all-sky, multiwavelength, and multiepoch observations. The VOs work out standards for efficient work with the databases, extraction, reduction and analysis of data, like Registries, Data Models, Uniform Content Descriptors (UCD), Data Access Layer (DAL), VO Query Language (ADQL), VOTable, VOPlot, Simple Image Access Protocol (SIAP), Simple Spectral Access Protocol (SSAP), etc. The Armenian Virtual Observatory (ArVO) project was created on the basis of the Digitized First Byurakan Survey (DFBS) to make a system for its efficient use and integrate the Armenian astronomy into the international one.
One of the main tasks for the ArVO is to create an efficient user interface for the DFBS. The usage of this database is being developed in the following way: the needed region of the DFBS plate with given sizes, and the corresponding region from DSS1 and DSS2 will be extracted, the 2D spectra of objects will be retrieved and compared with templates, the 1D spectra of objects will be available too, wavelength and intensity calibration, and a numerical classification will be made, the DFBS catalog data for objects will be given (position, magnitude, colors, types), other available data from web (SIMBAD/NED/MAPS/USNO-B1.0) will be provided, cross-matching with other catalogs will be carried out, and finally, the multiwavelength data for all objects of interest will be available.
ArVO was officially authorized as an International Virtual Observatories Alliance (IVOA) project in July 2005. ArVO includes also science development, as it is the actual goal of AVOs. It is the development of an automatic identification procedure for X-ray, IR and radio sources using the low-dispersion spectra and all other available databases; optical identification of ~100,000 X-ray, IR & radio sources; development of an automatic search procedure for modeled objects; automatic search for new bright AGN in DFBS/DSBS, etc.
Search for new bright QSOs by the core - host galaxy ratio
Though some 100,000 quasars are known, we are not complete with the bright ones. These are especially important for detailed studies, including their core - host galaxy relation. Surprisingly, 16th magnitude objects may still be found. The discovery of all bright quasars is really a problem, as there is not a single method allowing reveal them independent of their color, presence of radio and/or X-ray, etc. However, it seems the only feature typical for all of them is the presence of the host galaxy. We have studied the DSS2 BRI images for all 1193 objects having B<16.5 and/or z<0.3 from the Véron-Cetty and Véron catalog (2003) and found that about 80% of them have a point-like image in blue, but extended in red and IR, the host galaxies being mostly red. Moreover, the core is so weak in IR that only the host galaxy is observable. These objects may be easily distinguished by the core - host galaxy ratio if compared from the three colors. The objects being extended in B too, anyway may be distinguished by this ratio. Thus, a special technology using the multiband images allows reveal new quasars that could not be found by radio, X-ray or other features. A search with a goal to find all bright quasars in the region with DEC>0 and |b|>20 has been undertaken in Byurakan. The 2.6m telescope with the SCORPIO system is being used for the spectral identification of the candidates.
The inner structure of stellar jets
Line formation in multi-component stochastic media
Investigation of the large-scale space orientation model of the
extragalactic double radiosources by the inverse problems method
H.V. Pikichian, A.V. Kishinevskaya, T. Hovhannesyan
In frame of the symmetric model of the extragalactic double radiosources (EDR), the inverse problem of revealing of the large-scale space orientation of their radioaxes has been put forward and undergone analitical and numeric investigations. The simplifying natural assumptions allowed to bring the problem to a system of integral equations, which may be solved unanimously. In the simplest case, when a centrisymmetric orientation of radioaxes is assumed, the problem goes to a solution of simple non-linear system of ariphmetic equations. First, a numerical modelling of real and observed distributions of observable quantities has been done, then the ariphmetic system has been solved for the given model by the Monte-Carlo method. In a centrisymmetric simplest model, in this way the accuracy of the searched values of the derivable quantities has been estimated, depending on the degree of the statistical richness of the modelled "observational material". After such a test, the real observational material was reduced with the same algorithm. It is worth mentioning that an estimate close to one given formerly by Birch et al. was obtained for the angular coordinates of the center of anisotropy, and for the third coordinate, the distance of the center of anisotropy, all our calculations lead to inaccurate values. The last fact, probably leads to a real necessity for transition to calculations with axisymmetric model rather than a simple centrisymmetric anisotropy model.
Spectral studies of the FBS blue stellar objects
P.K. Sinamian, A.M. Mickaelian
Spectral observations of the First Byurakan Survey (FBS) blue stellar objects have been carried out since 1987 with a goal of classification, discovery of new interesting objects and study of the FBS sample in total. In 1987-1991, the Byurakan Observatory 2.6m telescope with the long-slit spectrograph UAGS was used. These photographic spectra were digitized by means of a professional scanner and reduced with MIDAS as for CCD spectra. Observations for new FBS objects, as well as repeated observations for confirmation and clarification of the classification were conducted in 1997-2000 with the BAO-2.6 and OHP-1.93 telescopes by means of modern equipment. Altogether, 485 spectra for 406 objects were obtained, mainly for objects in the FBS zones with central declinations +35, +39, and +43, as well as a number of objects were observed in zones with DEC>+61. The principles of digitization and follow-up automatic reduction of photographic spectra are discussed. The principles of object classification as for photographic spectra, so as for CCD spectra are worked out. New white dwarfs, hot subdwarfs, HBB stars, cataclysmic variables, planetary nebulae, as well as some extragalactic objects are revealed. The continuation of the survey for blue stellar objects is being carried out on the basis of the Digitized First Byurakan Survey (DFBS) spectra, and the selection and the preliminary classification of objects is much more efficient.