Research of the fine structure of the radio galaxy 3C 234 with radio interferometer URAN-2
The brief description and the basic characteristics of the radio interferometer URAN-2 aerial system, included in VLBI decameter system URAN, are presented. The research results of the 3C 234 angular structure with URAN system are submitted. The model of radiobrightness distribution of this source a...
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Головна астрономічна обсерваторія НАН України
2005
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| Цитувати: | Research of the fine structure of the radio galaxy 3C 234 with radio interferometer URAN-2 / R.V. Vashchishin, A.V. Megn, S.L. Rashkovsky, V.A. Shepelev, G.A. Inyutin, A.I. Brazhenko, V.G. Bulatsen// Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 75-77. — англ. |
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nasplib_isofts_kiev_ua-123456789-796072025-02-09T14:57:12Z Research of the fine structure of the radio galaxy 3C 234 with radio interferometer URAN-2 Vashchishin, R.V. Megn, A.V. Rashkovsky, S.L. Shepelev, V.A. Inyutin, G.A. Brazhenko, A.I. Bulatsen, V.G. MS1: Decameter Radioastronomy The brief description and the basic characteristics of the radio interferometer URAN-2 aerial system, included in VLBI decameter system URAN, are presented. The research results of the 3C 234 angular structure with URAN system are submitted. The model of radiobrightness distribution of this source at frequencies of 20 and 25 MHz is obtained. With the URAN-2 radio interferometer compact details in a radio galaxy have been found and their contribution to the general flow of a radio emission at decameter waves is determined. The effect of reabsorption in compact details (hot spots) is found and their true angular size are determined based on the research of the 3C234 spectrum. 2005 Article Research of the fine structure of the radio galaxy 3C 234 with radio interferometer URAN-2 / R.V. Vashchishin, A.V. Megn, S.L. Rashkovsky, V.A. Shepelev, G.A. Inyutin, A.I. Brazhenko, V.G. Bulatsen// Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 75-77. — англ. 0233-7665 https://nasplib.isofts.kiev.ua/handle/123456789/79607 en Кинематика и физика небесных тел application/pdf Головна астрономічна обсерваторія НАН України |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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DSpace DC |
| language |
English |
| topic |
MS1: Decameter Radioastronomy MS1: Decameter Radioastronomy |
| spellingShingle |
MS1: Decameter Radioastronomy MS1: Decameter Radioastronomy Vashchishin, R.V. Megn, A.V. Rashkovsky, S.L. Shepelev, V.A. Inyutin, G.A. Brazhenko, A.I. Bulatsen, V.G. Research of the fine structure of the radio galaxy 3C 234 with radio interferometer URAN-2 Кинематика и физика небесных тел |
| description |
The brief description and the basic characteristics of the radio interferometer URAN-2 aerial system, included in VLBI decameter system URAN, are presented. The research results of the 3C 234 angular structure with URAN system are submitted. The model of radiobrightness distribution of this source at frequencies of 20 and 25 MHz is obtained. With the URAN-2 radio interferometer compact details in a radio galaxy have been found and their contribution to the general flow of a radio emission at decameter waves is determined. The effect of reabsorption in compact details (hot spots) is found and their true angular size are determined based on the research of the 3C234 spectrum. |
| format |
Article |
| author |
Vashchishin, R.V. Megn, A.V. Rashkovsky, S.L. Shepelev, V.A. Inyutin, G.A. Brazhenko, A.I. Bulatsen, V.G. |
| author_facet |
Vashchishin, R.V. Megn, A.V. Rashkovsky, S.L. Shepelev, V.A. Inyutin, G.A. Brazhenko, A.I. Bulatsen, V.G. |
| author_sort |
Vashchishin, R.V. |
| title |
Research of the fine structure of the radio galaxy 3C 234 with radio interferometer URAN-2 |
| title_short |
Research of the fine structure of the radio galaxy 3C 234 with radio interferometer URAN-2 |
| title_full |
Research of the fine structure of the radio galaxy 3C 234 with radio interferometer URAN-2 |
| title_fullStr |
Research of the fine structure of the radio galaxy 3C 234 with radio interferometer URAN-2 |
| title_full_unstemmed |
Research of the fine structure of the radio galaxy 3C 234 with radio interferometer URAN-2 |
| title_sort |
research of the fine structure of the radio galaxy 3c 234 with radio interferometer uran-2 |
| publisher |
Головна астрономічна обсерваторія НАН України |
| publishDate |
2005 |
| topic_facet |
MS1: Decameter Radioastronomy |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/79607 |
| citation_txt |
Research of the fine structure of the radio galaxy 3C 234 with radio interferometer URAN-2 / R.V. Vashchishin, A.V. Megn, S.L. Rashkovsky, V.A. Shepelev, G.A. Inyutin, A.I. Brazhenko, V.G. Bulatsen// Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 75-77. — англ. |
| series |
Кинематика и физика небесных тел |
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2025-11-27T02:57:00Z |
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2025-11-27T02:57:00Z |
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| fulltext |
RESEARCH OF THE FINE STRUCTURE OF THE RADIO GALAXY 3C234
WITH RADIO INTERFEROMETER URAN-2
R. V. Vashchishin1, A. V. Megn2, S. L. Rashkovsky2, V. A. Shepelev2,
G. A. Inyutin2, A. I. Brazhenko1, V. G. Bulatsen1
1Gravimetrical Observatory, Institute of Geophysics, NAS of Ukraine
27/29 Myasoedova Str., 36029 Poltava, Ukraine
e-mail: vrsl@mail.ru
2Institute of Radio Astronomy, NAS of Ukraine
4 Chervonopraporna Str., Kharkiv, Ukraine
The brief description and the basic characteristics of the radio interferometer URAN-2 aerial sys-
tem, included in VLBI decameter system URAN, are presented. The research results of the 3C234
angular structure with URAN system are submitted. The model of radiobrightness distribution
of this source at frequencies of 20 and 25 MHz is obtained. With the URAN-2 radio interfer-
ometer compact details in a radio galaxy have been found and their contribution to the general
flow of a radio emission at decameter waves is determined. The effect of reabsorption in compact
details (hot spots) is found and their true angular size are determined based on the research of
the 3C 234 spectrum.
INTRODUCTION
The radio emission research of space radiation sources at the decameter waves known as one is connected with
the certain difficulties that is defined both of specificity of this range, and necessity of construction of the big
aerial systems insufficient in this range. Thus, obtained high angular resolution can be reached not by separate
tools, but with long-baseline interferometric systems, which for today are the most informative method of
researches. Having in order of NAS of Ukraine decree the unique VLBI system URAN, we can study the fine
structure of space radio sources at the decameter waves with 1′′ resolution.
In 2000 the construction, tests, and adjustment of the URAN-2 radio telescope included in this system
have been completed that has allowed us to use it more effectively both in structure interferometer, and for
the decision of independent radio astronomical tasks.
THE ARRAY OF RADIO TELESCOPE URAN-2
The URAN-2 radio telescope is situated in Stepanovka of Poltava region that is 153 km distance from UTR-2.
The URAN-2 aerial in comparison with other aerials of URAN system, provides the highest spatial filtration of
signals: on the azimuth A – up to 3.5◦, on the corner of place ε – up to 7◦. The resolution of an interferometer
on declination is provided by the aerial “north-south” of a radio telescope UTR-2 which has the beam 0.5◦
width in zenith at the frequency of 25 MHz.
The antenna is executed as multielement rectangular horizontal phasing array with the dimensions of
238×118 m. It consists of 512 elements. As an element of a array the two orthogonal vibrators are used,
located at an angle of 45◦ to meridian that enables to receive the two linear (circular) polarizations of a signal
and to take into account the influence of Faraday rotation of a polarization plane in interplanetary plasma and
ionosphere of the Earth.
For management by the directional diagram the time phasing method with the time delay lines for compen-
sation advancing of signals in the dipoles is applied. It allows us to receive the signals practically for the most
of the top hemisphere angles both in a wide band of frequencies, and simultaneously at the several different
frequencies.
The phasing system executed under multi-storey circuits, provides discrete management of a beam on two
angular coordinates such as l = cos ε · sin A and m = cos ε · cosA in the sector of ±1 for each of two linear
polarizations: 128 positions of a beam at the l coordinate and 64 positions of a beam at the m coordinate.
The basic characteristics of the URAN-2 array are shown in Fig. 1.
c© R. V. Vashchishin, A. V. Megn, S. L. Rashkovsky, V. A. Shepelev, G. A. Inyutin, A. I. Brazhenko, V. G. Bulatsen, 2004
75
a) array efficiency b) effective area
Figure 1. Dependencies of the array efficiency η and the effective area Aeff on the frequency for zenith direction
RESEARCH OF THE ANGULAR STRUCTURE OF THE RADIO GALAXY 3C 234
In the interferometer composition the URAN-2 provides an angular resolution about 4′′ at sensitivity about
12 Jy, that allows us to investigate the fine structure of a brightness distribution of many radio sources.
One of the sources which was investigated lately with a radio interferometer URAN-2 and which had the exp-
ressed compact details, was radio galaxy 3C 234, classified as classical double FR II object with a steep spectrum.
The structure of radio galaxy at the millimeter waves was represented rather complex and interesting, consisting
of strongly extended jets at which edges the hot spots were observed. The spacing of the centers of hot
spots was 110′′. At the centimeter and decimeter wavelengths the angular structure of radio galaxy has been
also determined in details well enough, but already in a meter range its structure has not been established.
In the most long-wave band i.e., the decameter one, the observations were carried out with two facilities of
the system URAN – URAN-1 and URAN-2 with D baselines of 42 and 153 km, respectively. The inter-
ferentional signals were formed by multiplication of signals of the URAN antennas with a signal of the antenna
“north–south” of the UTR-2 radio telescope.
During the observations using both facilities the oscillation of dependencies of visibility function on a hour
angle γ(T0) was presented. It is evidence of the interference in response to a minimum of two components of
model of brightness distribution occurs at decameter waves. The oscillations observable using the UTR-2 radio
interferometer indicated that the compact details (to sizes of which URAN-1 is not sensitive) are observed in
3C234 structure. The high frequency of these oscillations specified of the significant angle distance between
these details in space.
In connection with well-known difficulties of the observations at the decameter waves range and the “habits”
of URAN system, during observations of a source only the modules of visibility function were measured. It does
not allow us to use the methods of radiomaps construction by means of return Fourier transform used at high
frequencies. So, the interpretation of the received experimental data was carried out by the model approximation
method with a set of elliptic Gaussian components with different angular sizes and relationships of flows. It was
applied χ2 criterion in the degree of proximity measures of model to experiment.
To determine the initial conditions for search of models of 3C234 radiobrightness distribution at decameter
range, at the beginning it was necessary to define the model for frequency of 8 400 MHz. A dependence γ(T0) for
this model would coincide precisely with calculated γc(T0) based on radiomap at the same frequency. The one
general model of the brightness distribution was searched for four instanced values D/λ (URAN-1 – 3525 and
2820; URAN-2 – 12 692 and 10 153 at the frequencies of 25 MHz and 20 MHz, respectively). As a result
the optimal model at the frequency of 8 400 MHz has been determined as five-component, consisting of two
compact details and three extended, the greatest of which covers the central area of a galaxy, including its
nucleus.
For the further refinement of this model by the computering technique with reference to the obtained in
the decameter range experimental data, the optimal four-component model of brightness distribution consisting
of two compact and two extended details adjoining to them has been obtained. The parameters of the de-
rived model for the frequencies of 25 and 20 MHz are listed in Table 1, and the model is shown in Fig. 2 in
the background of the galaxy radiomap derived with VLA at the frequency of 8 400 MHz.
It will be interested to carry out the analysis of the radio galaxy 3C234 spectrum and in particular its
components, and as far as possible to specify the true sizes of compact details. The maximum of radiation at
76
Figure 2. Model of 3C 234 brightness distribution derived at the frequency of 25 MHz (dotted curves) in the background
of the 3C234 radiomap (see Table 1)
Table 1. Parameters of the models of 3C 234 radiobrightness distribution at decameter waves1
ν, MHz Component Δα′′
i Δδ′′i Si/S0 Δθ′′i max Δθ′′i min ψ◦
1 (S–W) 0 0 0.22±0.03 <2.3 <2.3 –
20 2 6.1±4.0 −0.4±13 0.33±0.06 35.7±6.0 9.2±2.6 0±40
3 83.7±6.0 34.2±20 0.4±0.05 37±10 10.9±4.5 51.8±25
4 (N–E) 96.3±2.2 46±14 0.05±0.02 <2.3 <2.3 –
1 (S–W) 0 0 0.25±0.03 <2.3 <2.3 –
25 2 6.1±4.6 −0.4±12 0.33±0.06 29.6±6.5 7.6±2.8 0±36
3 83.7±3.5 34.2±13.5 0.36±0.05 37±6 10.9±2.6 51.8±27.5
4 (N–E) 98.8±1.3 45.6±7.7 0.06±0.02 <2.3 <2.3 –
the frequency about 50 MHz is observed for the compact components spectra. The various mechanisms are
examined which could responsible for the falling of the spectral density of radiation lower than the frequency of
a maximum. As a result was found out that the spectra of compact components coincide in the best way with
the derived spectrum calculated for reabsorption. This one has enabled us to determine the own true angular
sizes of the compact components at the decameter wavelengths: towards the North–East is 0.27 ′′; towards
the South–West is 0.55′′ 2.
Thus, the two compact details of the radio galaxy 3C 234 have been allocated with the radio interferome-
ter URAN-2 that has allowed us to establish a complete brightness distribution at the decameter wavelength,
namely: it was found out that the radioimage of 3C234 in the centimeter and decimeter wave bands in the cer-
tain extent is kept in the decameter range. It first of all touches on two compact components, their relative
coordinates and angular sizes, and also the coordinates of the centers and orientation of the axes of two ex-
tended components located near to compact ones. The basic changes in brightness distribution of a source
during the frequency reduction up to decameter waves consist of some times increasing of the angular sizes
of extended components. The more essentially is an absence of an appreciable radio-frequency radiation of
the most extended component of the high-frequency radioimage covering the central area of a galaxy with its
nucleus and providing a significant part of a source total radiation at high frequencies.
1 Δα′′
i and Δδ′′i are the coordinates of the centers of components in arcsec (Δαsw = Δδsw = 0); Si/S0 is relative magnitude
of the components radioemission spectral density; Δθ′′i max and Δθ′′i min are the maximal and minimal angular sizes of components
in arcsec; ψ is an angle of orientation of the main axis of components in grades (towards the West).
2 The sizes seen on the Earth’s surface and which are already dispersion-stricken in the interstellar and interplanetary medium
are measured from the radio interferometric observations of compact details, but from spectral measurements their true sizes are
determined when the reabsorption effect is available.
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