Extragalactic Radio Sources: Jet/Lobe Internal Pressure and Consequences

Physical Science International Journal ◽

10.9734/psij/2021/v25i230241 ◽

2021 ◽

pp. 20-25

Author(s):

Ezeugo Jeremiah Chukwuemerie

Keyword(s):

Internal Pressure ◽

Analytical Methods ◽

Ambient Medium ◽

Source Size ◽

Central Core ◽

Radio Sources ◽

Medium Density ◽

Host Galaxies ◽

Extragalactic Radio Sources

In this work, we use analytical methods to describe expansion of Extragalactic Radio Sources (EGRS). Result shows that source size expansion depends on the following parameters: age of the source, lobe internal pressure, ambient medium density, and angle of observation. Moreover, from the analyses, we have shown that the obtained results, and , suggestively implies that and . This shows that since , jet internal pressure exceeds the lobe’s internal pressure. Therefore, for a typical EGRS, this simply indicates that ambient medium density is higher in the jet region than in the region of the lobe. This is expected since the ambient density thins out from the central core to the region where lobe is located. It is in consonance with the notion that for large extended EGRS, lobes are located outside the host galaxies rather than within the host galaxies. Moreover, we can conclude from these results that compact steep spectrum sources have denser ambient medium than their more extended counterparts.

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The Distant DRAGNs Survey

Symposium - International Astronomical Union ◽

10.1017/s0074180900081675 ◽

1996 ◽

Vol 175 ◽

pp. 513-514

Author(s):

J. D. B. Law-Green

Keyword(s):

Flux Density ◽

Ambient Medium ◽

High Redshift ◽

Galactic Nuclei ◽

Cosmological Evolution ◽

Radio Sources ◽

Number Density ◽

Extragalactic Radio Sources ◽

Matched Samples

DRAGNs (Double Radio sources Associated with Galactic Nuclei, Leahy 1991) are the class of powerful extragalactic radio sources thought to be produced by the interaction of a jet with the ambient medium. They exhibit strong cosmological evolution in comoving number density; at z ≃ 2 the “classical double” FR II DRAGNs were ≃ 1000 times as common as they are now (Dunlop & Peacock 1990).To understand this, systematic studies of complete DRAGN samples at low and high z and differing levels of flux density are required, in order to resolve the P – z ambiguity. The Distant DRAGNs Survey is a long-term project to image with the VLA and MERLIN, matched samples of DRAGNs at high redshift.

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9.10. The cause of the spectral turnover in the GPS source 0108+388: free-free absorption or SSA?

Symposium - International Astronomical Union ◽

10.1017/s0074180900085375 ◽

1998 ◽

Vol 184 ◽

pp. 401-402

Author(s):

J. M. Marr ◽

F. Crawford ◽

G. B. Taylor

Keyword(s):

Magnetic Fields ◽

Radio Source ◽

High Frequency ◽

Radio Sources ◽

Host Galaxies ◽

Ionized Gas ◽

High Frequencies ◽

Extragalactic Radio Sources ◽

Competing Models ◽

Frequency Radiation

The radio source 0108 + 388 is a canonical example of a class of extragalactic radio sources, referred to as Gigahertz-Peaked Spectrum (GPS) sources, whose spectra peak at high frequencies. There are two competing models for the cause of the high frequency turnover: free-free absorption (f-f) of the lower frequency radiation by ionized gas in the host galaxies (e.g. van Breugel 1984), or synchrotron self-absorption (SSA) due to exceptionally large magnetic fields, (e.g. Hodges, Mutel, & Phillips 1984).

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Compact Steep-Spectrum Radio Sources and Ambient Medium Density

International Journal of Astrophysics and Space Science ◽

10.11648/j.ijass.20150301.11 ◽

2015 ◽

Vol 3 (1) ◽

pp. 1

Author(s):

Ezeugo Jeremiah Chukwuemerie

Keyword(s):

Ambient Medium ◽

Radio Sources ◽

Medium Density ◽

Spectrum Radio

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Depolarization of Extragalactic Radio Sources

Symposium - International Astronomical Union ◽

10.1017/s0074180900028096 ◽

1982 ◽

Vol 97 ◽

pp. 339-340

Author(s):

M. Inoue ◽

H. Tabara

Keyword(s):

Faraday Rotation ◽

Source Size ◽

The Other ◽

Radio Sources ◽

Half Maximum ◽

Radio Luminosity ◽

Extragalactic Radio Sources ◽

Other Hand ◽

Percentage Polarization

In the last decade correlations of the depolarization parameter λd with several parameters, i.e., the radio luminosity L, redshift z, and source size D have been investigated by several authors, where λd is the wavelength at which the percentage polarization drops to its half maximum. Kronberg ET AL. (1972) first pointed out that λd decreases with increasing z, while Morris and Tabara (1973) showed that λd increases with L and suggested that the depolarization is due to the internal Faraday rotation within radio sources. Conway ET AL.(1974), on the other hand, suggested that the λd-(1+z) relation is primary. Recently, Cohen (1979) showed that the λd-z relation may be the remnant of the physically meaningful relation λd-L, though the former is statistically real.

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A GENERAL SELF-SIMILAR MODEL AND THE P-D DIAGRAM OF EXTRAGALACTIC RADIO SOURCES

International Journal of Modern Physics D ◽

10.1142/s0218271807010158 ◽

2007 ◽

Vol 16 (02n03) ◽

pp. 381-390

Author(s):

A. P. LIMA ◽

J. C. CARVALHO ◽

C. P. O'DEA

Keyword(s):

Power Law ◽

Ambient Medium ◽

Great Majority ◽

Conservation Equation ◽

Analytical Models ◽

Host Galaxy ◽

Constant Density ◽

Radio Sources ◽

Equilibrium Equations ◽

Extragalactic Radio Sources

The great majority of analytical models for extragalactic radio sources suppose self-similarity and can be classified into three types. We have developed a model that represents a generalization of most models found in the literature and show that these three types are particular cases. The model assumes that the area of the head of the jet varies with the jet size according to a power law and the jet luminosity is a function of time. As is usually done, the basic hypothesis is that there is an equilibrium between the pressure exerted both by the head of the jet and the cocoon walls and the ram pressure of the ambient medium. The equilibrium equations and energy conservation equation allow us to express the size and width of the source and the pressure in the cocoon as a power law and find the respective exponents. Once we find these exponents, we can determine the initial values of the source size, the cocoon radius and of the pressure inside the cocoon. We also suppose that, near the nucleus, the jet propagates in a constant density atmosphere and, as it leaves the central region of the host galaxy, it propagates in a decaying atmosphere. All these assumptions can be used to calculate the evolution of the source radio luminosity allowing us to draw a P-D diagram. This can then be compared with the observed P-D diagram of both compact (GPS and CSS) and extended sources from the 3CR catalogue. The comparison makes it possible to determine the various parameters of the model and understand the physical processes involved in the evolution of extragalactic radio sources.

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