Peculiar morphologies of extended extragalactic radio sources from numerical simulations
Among the extragalactic radio sources there are objects with unusual morphologies. We investigated the possibility that the propagation of jets in a stratified distribution of density may produce such effects. A numerical setup was worked out and hydrodynamical 2D simulations were performed using th...
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| Опубліковано в: : | Advances in Astronomy and Space Physics |
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| Дата: | 2011 |
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Advances in astronomy and space physics
2011
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| Цитувати: | Peculiar morphologies of extended extragalactic radio sources from numerical simulations / D.A. Lacatus, M. Badea, A.R. Paraschiv, O. Tesileanu // Advances in Astronomy and Space Physics. — 2011. — Т. 1., вип. 1-2. — С. 27-29. — Бібліогр.: 6 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859712771623485440 |
|---|---|
| author | Lacatus, D.A. Badea, M. Paraschiv, A.R. Tesileanu, O. |
| author_facet | Lacatus, D.A. Badea, M. Paraschiv, A.R. Tesileanu, O. |
| citation_txt | Peculiar morphologies of extended extragalactic radio sources from numerical simulations / D.A. Lacatus, M. Badea, A.R. Paraschiv, O. Tesileanu // Advances in Astronomy and Space Physics. — 2011. — Т. 1., вип. 1-2. — С. 27-29. — Бібліогр.: 6 назв. — англ. |
| collection | DSpace DC |
| container_title | Advances in Astronomy and Space Physics |
| description | Among the extragalactic radio sources there are objects with unusual morphologies. We investigated the possibility that the propagation of jets in a stratified distribution of density may produce such effects. A numerical setup was worked out and hydrodynamical 2D simulations were performed using the PLUTO code. We carried out a parametric study of a jet launched along the main axis of the mass distribution in order to obtain important sideways features.
|
| first_indexed | 2025-12-01T06:25:30Z |
| format | Article |
| fulltext |
Peculiar morphologies of extended extragalactic radio sources from
numerical simulations
D. A. Lacatus, M. Badea, A. R. Paraschiv, O. Te³ileanu
Research Center for Atomic Physics and Astrophysics Faculty of Physics, University of Bucharest,
Atomistilor st., 405, 077125, Magurele - Ilfov, Romania
lacatus.dana@gmail.com
Among the extragalactic radio sources there are objects with unusual morphologies. We investigated the
possibility that the propagation of jets in a strati�ed distribution of density may produce such e�ects. A
numerical setup was worked out and hydrodynamical 2D simulations were performed using the PLUTO code.
We carried out a parametric study of a jet launched along the main axis of the mass distribution in order to
obtain important sideways features.
Introduction
Active galaxies have active nuclei (AGN) in their cores, which are compact regions with a luminosity much
higher than normal over a wide range of the electromagnetic spectrum. Early observations of twin lobes
of extended radio sources, which were later associated with galaxies at cosmological distances, provided an
evidence of highly collimated jets leading to the conclusion that such jets are huge in size, up to megaparsecs,
and are highly energetic. The energy release is beyond that which can be attributed to normal processes
from stars, interstellar medium and their interaction, therefore the primary source of energy is considered
to be a result of mass accretion onto a supermassive black hole in the center of the host galaxy. A typical
example of such objects is Cygnus A radio galaxy (see [3] for details).
The classi�cation of extended radio sources is made based on observational characteristics. The main
categories are (see e. g. [6]):
- Seyfert galaxies (type I and II)
- Radio galaxies (Fanaro�-Riley or FR I and II types)
- Quasars (radioloud and radioquiet)
- Blazars.
Radio galaxies with moderate emission lead to distortions observed in FR II jets. These distortions can
be classi�ed as follows:
- C-shaped, or C mirror-symmetric, when the two jets bend in the same direction;
- X or Z-shaped, center-symmetric, when the jets bend in opposite directions, making up to about 7% of
FR II radio sources. Some of them also have a di�use emission along the second axis [1].
The generally accepted origin of such relativistic jets is the central supermassive black hole, surrounded by
an accretion disc, which gives rise to two opposite jets. The variety of morphologies can be explained if one
considers di�erent positions of the source axis with regard to our line of sight. These jets are believed to be
made up of a mixture of electrons and positrons/protons, highly collimated due to pressure con�nement and
having supersonic out�ow velocities. The extreme regions of the jets are large structures, so called cocoons,
which correspond to the observed lobes of radio emission. The appearance of these cocoons is di�erent for
the FR I and FR II sources, in terms of the position of the region of emission maximum.
Setting up the problem
The peculiar morphologies observed in extragalactic radio sources are yet to be fully understood, but in
the case of many X-shaped radio sources there is a strong dependence on the properties of a host galaxy.
These sources tend to be located in elliptical galaxies, with the jet axis close to the main axis of the density
27
Advances in Astronomy and Space Physics D. A. Lacatus, M. Badea, A. R. Paraschiv, O. Te³ileanu
Table 1: Ratio between the jet's dimension on y and x axis for di�erent combinations of parameters.
simulation M: 100 100 100 150 150 150 150 200 200 200 200
ν: 0.01 0.005 0.001 0.01 0.005 0.001 0.0005 0.01 0.005 0.001 0.0005
∆ y/∆ x 3.33 2.85 2 3.33 3.07 2.22 1.81 1.9 3.08 2.22 2
distribution. For the present study we performed numerical 2D hydro-dynamical simulations by means of
PLUTO code [5].
This code is a multi-physics, multi-algorithm, high-resolution code, suitable for time-dependent, explicit
computations of highly supersonic �ows in the presence of strong discontinuities, and it can be applied in
di�erent modes, i.e., classical, relativistic unmagnetized, and magnetized �ows. The code is structured in
a modular way, allowing a new module to be easily incorporated. This �exibility turns out to be quite
important, since many aspects of computational �uid dynamics are still in rapid development. Besides, the
advantage o�ered by a multiphysics, multisolver code is also to supply the user with the most appropriate
algorithms and, at the same time, provide interscheme comparison for a better veri�cation of the simulation
results. PLUTO is entirely written in C programming language and can run on either single processor or
parallel machines. The code has already been successfully applied for stellar and extragalactic jets. For the
performed simulations we used a cylindrical symmetry on a uniform grid, with 256 × 256 integration cells.
The results were then plotted and their characteristics were analyzed using Interactive Data Language
(IDL).
The supersonic jet was inserted along the main axis of the ellipsoidal strati�ed medium, described by a
King density distribution [4], that best describes elliptical galaxies which are the hosts of such jets. The
parameters that characterize a jet are the Mach number M with respect to the sound speed in the external
medium (100, 150 and 200) and ν � the ratio between the jet density and the density of the external gas
distribution in the central point (0.01, 0.001, 0.005 and 0.0005). A conclusion that could be drawn from the
simulations performed in the last decades was that the jets are underdensed with respect to the ambient
medium. Both jets of a pair were simulated, with slightly di�erent velocities, in order to avoid the numerical
re�ection e�ects in the symmetry plane.
Results and conclusions
Using all possible combinations of the considered parameters, we performed 12 simulations. (For a typical
example of the density distribution see Figure 1, right). The evolution in the normalized time is presented
Figure 1: Left : Total energy to kinetic energy ratio for M=100 and di�erent values of ν: 0.0005(1), 0.001(2),
0.005(3), 0.01(4). Right : Density distribution of a typical jet.
28
Advances in Astronomy and Space Physics D. A. Lacatus, M. Badea, A. R. Paraschiv, O. Te³ileanu
Table 2: Ratio between the jet's dimension on y and x axis taken at di�erent time steps for a given simulated
jet.
∆y/∆x 1.66 1.4 1.66 1.44 1.5 1.33 1.58 1.5 1.53 1.62 1.56 1.5 1.52 1.59
Frame 10 20 30 40 50 60 70 80 90 100 110 120 130 140
for each of them, up to the moment the jet head exits the de�ned domain, as well as the evolution in time
of the ratio between the total energy and the kinetic energy.
Comparative approach of the ratio between the total energy and the kinetic energy for a given Mach
number leads to the conclusion that this ratio decreases with the decrease of the density ratio. (See Figure 1,
left) The reason why such a behavior is present is due to the fact that with the increase of density ratio
higher amounts of matter are set in motion, and the velocity gradient along the jet decreases (as the heavier
matter transports momentum more e�ciently), leading to the increase of kinetic energy ratio to the total
energy.
For each simulation we computed the ratio between the jet's dimensions on y and x (Z and R axis in
cylindrical coordinates); we found that generally this ratio has similar values for a given density ratio (See
Table 1).
Taking this ratio at di�erent time steps for one given jet we founded similar values, all within the range
1.4− 1.66. These values can be used for characterizing the structure, which means that the jet is stable for
a given set of parameters (See Table 2).
The sample of 9 X-shaped radio sources with su�cient extension of the secondary axis and reliable
observations of the host galaxies by HST is presented and discussed in [1]. Recently, a new set of X-shaped
radio sources candidates was proposed in [2], although not for all of them optical counterparts of relevant
quality are available.
Based on the performed simulations we can conclude that:
- The morphology of the jet depends greatly on the considered parameters.
- A jet launched along (or very close to) the main axis of the host galaxy's mass distribution may produce
important sideways features, that might correspond to the �wings� of the X-shaped structures observed.
- The possibility to get �wing-like� structures increases for fast, low-density jets.
- The ratio between the total energy and the kinetic energy also varies with the given parameters � steeper
decrease with increased Mach numbers.
This work is thus a further proof for the validity of the hypothesis proposed in [1], on the formation of
the X-shaped radio sources due to a particular geometrical con�guration of the collimated ejection axis and
the host galaxy.
Acknowledgement
The authors would like to thank Prof. Dr. Mircea Rusu for inspiring discussions. OT acknowledges
support from CNCSIS, contract RP no. 4/1.07.2009.
References
[1] Capetti A., Zam�r S., Rossi P. et al. Astron. & Astrophys., V. 394, pp. 39-45 (2002)
[2] Cheung C. C. Astron. J., V. 133, pp. 2097-2121 (2007)
[3] Ferrari A. Ann. Rev. Astron. Astrophys., V. 36, pp. 539-598 (1998)
[4] King I. Astron. J., V. 67, p. 471 (1962)
[5] Mignone A., Bodo G., Massaglia S. et al. Astrophys. J. Suppl. Ser., V. 170, pp. 228-242 (2007)
[6] Tesileanu O. Romanian Reports in Physics, V. 62, No. 1, pp. 202-208 (2010)
29
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| id | nasplib_isofts_kiev_ua-123456789-118977 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| isbn | 987-966-439-367-3 |
| language | English |
| last_indexed | 2025-12-01T06:25:30Z |
| publishDate | 2011 |
| publisher | Advances in astronomy and space physics |
| record_format | dspace |
| spelling | Lacatus, D.A. Badea, M. Paraschiv, A.R. Tesileanu, O. 2017-06-02T18:30:58Z 2017-06-02T18:30:58Z 2011 Peculiar morphologies of extended extragalactic radio sources from numerical simulations / D.A. Lacatus, M. Badea, A.R. Paraschiv, O. Tesileanu // Advances in Astronomy and Space Physics. — 2011. — Т. 1., вип. 1-2. — С. 27-29. — Бібліогр.: 6 назв. — англ. 987-966-439-367-3 https://nasplib.isofts.kiev.ua/handle/123456789/118977 Among the extragalactic radio sources there are objects with unusual morphologies. We investigated the possibility that the propagation of jets in a stratified distribution of density may produce such effects. A numerical setup was worked out and hydrodynamical 2D simulations were performed using the PLUTO code. We carried out a parametric study of a jet launched along the main axis of the mass distribution in order to obtain important sideways features. The authors would like to thank Prof. Dr. Mircea Rusu for inspiring discussions. OT acknowledges support from CNCSIS, contract RP no. 4/1.07.2009. en Advances in astronomy and space physics Advances in Astronomy and Space Physics Peculiar morphologies of extended extragalactic radio sources from numerical simulations Article published earlier |
| spellingShingle | Peculiar morphologies of extended extragalactic radio sources from numerical simulations Lacatus, D.A. Badea, M. Paraschiv, A.R. Tesileanu, O. |
| title | Peculiar morphologies of extended extragalactic radio sources from numerical simulations |
| title_full | Peculiar morphologies of extended extragalactic radio sources from numerical simulations |
| title_fullStr | Peculiar morphologies of extended extragalactic radio sources from numerical simulations |
| title_full_unstemmed | Peculiar morphologies of extended extragalactic radio sources from numerical simulations |
| title_short | Peculiar morphologies of extended extragalactic radio sources from numerical simulations |
| title_sort | peculiar morphologies of extended extragalactic radio sources from numerical simulations |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/118977 |
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