scholarly journals Parsec-scale Radio Structure of 14 Fanaroff–Riley Type 0 Radio Galaxies

2018 ◽  
Vol 863 (2) ◽  
pp. 155 ◽  
Author(s):  
X.-P. Cheng ◽  
T. An
Keyword(s):  
Radio Galaxies ◽  
Radio Structure

scholarly journals A Novel Method for Estimating the Ambient Medium Density Around Distant Radio Sources from Their Observed Radio Spectra

2021 ◽  
Vol 922 (2) ◽  
pp. 197
Author(s):  
Anna Wójtowicz ◽  
Łukasz Stawarz ◽  
Jerzy Machalski ◽  
Luisa Ostorero
Keyword(s):  
Radio Emission ◽  
Ambient Medium ◽  
Radio Galaxies ◽  
Radiative Properties ◽  
Radio Continuum ◽  
Physical Parameters ◽  
Radio Sources ◽  
Data Set ◽  
Radio Structure ◽  
5 Ghz

Abstract The dynamical evolution and radiative properties of luminous radio galaxies and quasars of the FR II type, are well understood. As a result, through the use of detailed modeling of the observed radio emission of such sources, one can estimate various physical parameters of the systems, including the density of the ambient medium into which the radio structure evolves. This, however, requires rather comprehensive observational information, i.e., sampling the broadband radio continua of the targets at several frequencies, and imaging their radio structures with high resolution. Such observations are, on the other hand, not always available, especially for high-redshift objects. Here, we analyze the best-fit values of the source physical parameters, derived from extensive modeling of the largest currently available sample of FR II radio sources, for which good-quality multiwavelength radio flux measurements could be collected. In the analyzed data set, we notice a significant and nonobvious correlation between the spectral index of the nonthermal radio emission continuum, and density of the ambient medium. We derive the corresponding correlation parameters, and quantify the intrinsic scatter by means of Bayesian analysis. We propose that the discovered correlation could be used as a cosmological tool to estimate the density of ambient medium for large samples of distant radio galaxies. Our method does not require any detailed modeling of individual sources, and relies on limited observational information, namely, the slope of the radio continuum between the rest-frame frequencies 0.4 and 5 GHz, possibly combined with the total linear size of the radio structure.

scholarly journals VLBI Cores in a Sample of Radio Galaxies

1988 ◽  
Vol 129 ◽  
pp. 75-76
Author(s):  
G. Comoretto ◽  
L. Feretti ◽  
G. Giovannini
Keyword(s):  
Statistical Study ◽  
Dynamic Range ◽  
Total Sample ◽  
Radio Galaxies ◽  
Log P ◽  
Complete Sample ◽  
Radio Structure ◽  
First Results ◽  
5 Ghz ◽  
Radio Power

We present the first results of a statistical study of the milliarcsec structure in a complete sample of radio galaxies. We have selected from the B2 and 3CR samples of galaxies the sources which present, at the VLA or WSRT angular resolution, an unresolved core with a flux density at 5 GHz Sc ≥ 100 mJy. The total sample consists of 30 radio galaxies, 17 from the B2 and 13 from the 3CR catalog. This complete sample covers a range of total radio power at 408 MHz log P = 23.5 – 26.5 W/Hz (low-intermediate luminosity). The radio structure of these sources on the arcsec-arcmin scale is well known, thanks to good dynamic range VLA and/or WSRT maps; a large variety of structures is present in the sample, from classical doubles to head-tail sources; flat, inverted and steep spectrum cores are also present.

scholarly journals The pc-scale radio structure of MIR-observed radio galaxies

2018 ◽  
Vol 18 (9) ◽  
pp. 108
Author(s):  
Ye Yuan ◽  
Min-Feng Gu ◽  
Yong-Jun Chen
Keyword(s):  
Radio Galaxies ◽  
Radio Structure

scholarly journals On the Unification of Radio Galaxies and Quasars

1994 ◽  
Vol 159 ◽  
pp. 501-501
Author(s):  
Krzysztof T. Chyzy
Keyword(s):  
Radio Galaxies ◽  
Linear Size ◽  
Expansion Velocity ◽  
Evolutionary Patterns ◽  
Consistency Test ◽  
Radio Structure ◽  
Size Evolution ◽  
The Asymmetry ◽  
Asymmetry Parameters ◽  
Independent Parameters

A comparison of the projected linear size evolution of extended quasars and radio galaxies are often used as a test of the radio galaxy - quasar unification schemes. If both the mentioned categories of radio sources differ to an observer only due to the various viewing directions, then their radio linear sizes are expected to evolve with redshift in the same way (Gopal-Krishna & Kulkarni, 1992). However, apart from the simplest linear size parameter L we can still determine two independent parameters assessing the asymmetry of the radio structure: Q - the arm lengths ratio; M - misalignment, which measures the apparent bending, and defined as the ratio of the displacement of the core from the source axis to the linear size. The asymmetry parameters Q and M can also be a powerful tool in the consistency test for the orientation based unification scheme as their evolutionary patterns should be the same for radio galaxies and quasars. Contrary to the linear size, they are not sensitive to the simple homological rescaling of the whole structure and hence to the age or expansion velocity of the structure.

scholarly journals Radio Observations of Moderately Compact Steep Spectrum Sources

1989 ◽  
Vol 134 ◽  
pp. 537-538
Author(s):  
Chidi Akujor ◽  
I.W.A. Browne ◽  
P.N. Wilkinson
Keyword(s):  
Radio Galaxies ◽  
Radio Spectrum ◽  
List Type ◽  
Type Number ◽  
Radio Observations ◽  
Radio Structure ◽  
Clear Cut ◽  
Wide Range ◽  
Compact Sources

It is now common practice for objects with a steep radio spectrum and compact radio structure to be lumped together and called compact steep spectrum (CSS) sources (Peacock and Wall, 1982; van Breugel, 1984 Fanti et al. 1985). This rather arbitrary categorisation results in the class containing sources with a wide range of structures, from core-jet or complex (e.g. 3C147,3C48), small classical doubles (e.g. 3C237, 3C241), to VLBI compact doubles (e.g. CTD93; Phillips and Mutel, 1982). Some of the questions we are asking include: (a)Are compact sources intrinsically small, or do they appear small because they are seen in projection?(b)Why are structures in compact radio galaxies and compact radio quasars different? Wilkinson et al. (1984) and Spencer et al (1988, in preparation)have shown that there appears to be a ‘clear-cut’ difference in morphology between quasar CSS and galaxy CSS, with quasars showing more distortions while galaxies tend to be doubles. But is this trend present even in their slightly more-extended counterparts?

scholarly journals X-shaped Radio Galaxies: Optical Properties, Large-scale Environment, and Relationship to Radio Structure

2019 ◽  
Vol 887 (2) ◽  
pp. 266 ◽  
Author(s):  
Ravi Joshi ◽  
Gopal Krishna ◽  
Xiaolong Yang ◽  
Jingjing Shi ◽  
Si-Yue Yu ◽  
...  
Keyword(s):  
Optical Properties ◽  
Large Scale ◽  
Radio Galaxies ◽  
Radio Structure

scholarly journals VLA Images of Two Extended Radio Galaxies

2002 ◽  
Vol 199 ◽  
pp. 193-194
Author(s):  
W. Junor ◽  
F. Mantovani ◽  
R. Morganti ◽  
L. Padrielli
Keyword(s):  
Radio Source ◽  
Low Frequency ◽  
Detection Limits ◽  
Radio Galaxies ◽  
Radio Structure ◽  
Polarization Effects ◽  
Compact Component ◽  
Instrumental Polarization ◽  
Extended Radio

There is some evidence from earlier studies that the two sources 0235 — 197 and 1203 + 043 exhibit low frequency (< 1 GHz) variability. This work shows that both sources have linear polarizations, if any, below the detection limits at 320 MHz, so we cannot explain the variability as being due to instrumental polarization effects as has been suggested for 3C159. Refractive scintillation may be the cause of the variability in 0235—197. The radio source 1203+043 lacks any bright compact component thereby ruling out a refractive scintillation mechanism for its variability. Consequently, it is possible that claims of variability in this source are spurious. However, the 320 MHz VLA observations show that 1203+043 has an ‘X'-shaped radio structure.

scholarly journals Optical Properties of the Radio Source B2 0828+32

1996 ◽  
Vol 175 ◽  
pp. 254-255
Author(s):  
M.-H. Ulrich-Demoulin ◽  
J. Rönnback
Keyword(s):  
Optical Properties ◽  
Radio Source ◽  
Spectral Index ◽  
Surface Brightness ◽  
Gravitational Interaction ◽  
Radio Galaxies ◽  
Host Galaxy ◽  
Radio Structure ◽  
Close Pair ◽  
Different Ages

A small number of radio galaxies have two sets of classical double radio lobes with the radio axes aligned in different directions. Furthermore differences in the properties of the radio lobes such as the surface brightness and spectral index indicate that the two sets of double radio structure have different ages. The radio ejection axis has therefore changed direction with time. In the first two known radio galaxies of this type, 3C 315 and B2 0055+26, the host galaxy is a member of a close pair of ellipticals in a common optical envelope suggesting that the complex radio structure is caused by gravitational interaction.

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