scholarly journals An X‐Ray Study of Magnetic Field Strengths and Particle Content in the Lobes of FR II Radio Sources

2005 ◽  
Vol 626 (2) ◽  
pp. 733-747 ◽  
Author(s):  
J. H. Croston ◽  
M. J. Hardcastle ◽  
D. E. Harris ◽  
E. Belsole ◽  
M. Birkinshaw ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Radio Sources ◽  
Particle Content ◽  
X Ray ◽  
Field Strengths

scholarly journals Magnetic Fields & Ionized Gas in Elliptical Galaxy Halos

1990 ◽  
Vol 140 ◽  
pp. 459-462
Author(s):  
Richard G. Strom
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Elliptical Galaxy ◽  
Radio Sources ◽  
Early Type ◽  
Ionized Gas ◽  
X Ray ◽  
Galaxy Halos ◽  
Field Strengths

Faraday depolarization estimates of thermal densities within the components of double radio sources agree well with estimates from X-ray observations of hot halos around early-type galaxies, provided magnetic field strengths are close to their equipartition values. Internal Faraday dispersion is the main cause of the depolarization observed.

scholarly journals Magnetic Field Strengths of GPS Radio Sources

1999 ◽  
Vol 194 ◽  
pp. 324-326
Author(s):  
V. G. Panajyan
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
Radio Sources ◽  
Spectral Indices ◽  
The Past ◽  
Spectrum Radio ◽  
Field Strengths

GHz peaked spectrum radio sources (GPS) are believed to be a subclass of compact steep spectrum radio sources (CSS) with high frequency spectral indices α < −0.5 (5 ˜ vα), linear sizes of pc to kpc scale and turnover spectra near 1GHz. Due to the work of many radioastronomers during the past two decades many properties of CSS and GPS radio sources at present are known (O'Dea,C.P. et al.1998, and references therein).

scholarly journals Extragalactic megahertz-peaked spectrum radio sources at milliarcsecond scales

2019 ◽  
Vol 628 ◽  
pp. A56 ◽  
Author(s):  
M. A. Keim ◽  
J. R. Callingham ◽  
H. J. A. Röttgering
Keyword(s):  
Magnetic Field ◽  
Spectral Characteristics ◽  
Galactic Nuclei ◽  
Radio Sources ◽  
Long Baseline ◽  
Spectrum Radio ◽  
Spectral Peaks ◽  
Murchison Widefield Array ◽  
Very Long Baseline Array ◽  
Field Strengths

Extragalactic peaked-spectrum radio sources are thought to be the progenitors of larger, radio-loud active galactic nuclei (AGN). Synchrotron self-absorption (SSA) has often been identified as the cause of their spectral peak. The identification of new megahertz-peaked spectrum sources from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey provides an opportunity to test how radio sources with spectral peaks below 1 GHz fit within this evolutionary picture. We observed six peaked-spectrum sources selected from the GLEAM survey, three that have spectral characteristics which violate SSA and three that have spectral peaks below 230 MHz, with the Very Long Baseline Array at 1.55 and 4.96 GHz. We present milliarcsecond resolution images of each source and constrain their morphology, linear size, luminosity, and magnetic field strength. Of the sources that are resolved by our study, the sources that violate SSA appear to be compact doubles, while the sources with peak frequencies below 230 MHz have core-jet features. We find that all of our sources are smaller than expected from SSA by factors of ≳20. We also find that component magnetic field strengths calculated from SSA are likely inaccurate, differing by factors of ≳5 from equipartition estimates. The calculated equipartition magnetic field strengths more closely resemble estimates from previously studied gigahertz-peaked spectrum sources. Exploring a model of the interaction between jets and the interstellar medium, we demonstrate that free-free absorption (FFA) can accurately describe the linear sizes and peak frequencies of our sources. Our findings support the theory that there is a fraction of peaked-spectrum sources whose spectral peaks are best modeled by FFA, implying our understanding of the early stages of radio AGN is incomplete.

scholarly journals Constraints on the Cluster Environments and Hot Spot Magnetic Field Strengths of the Radio Sources 3C 280 and 3C 254

2003 ◽  
Vol 584 (2) ◽  
pp. 643-656 ◽  
Author(s):  
Megan Donahue ◽  
Ruth A. Daly ◽  
Donald J. Horner
Keyword(s):  
Magnetic Field ◽  
Hot Spot ◽  
Radio Sources ◽  
Field Strengths

scholarly journals XMM Observation of the Galaxy Cluster Abell 514

2006 ◽  
Vol 2 (S235) ◽  
pp. 256-256
Author(s):  
J. Weratschnig ◽  
S. Schindler ◽  
M. Gitti
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Galaxy Cluster ◽  
Radio Sources ◽  
X Ray ◽  
Rotation Method ◽  
The Galaxy ◽  
Interesting Object ◽  
The Magnetic Field

AbstractWe present XMM-Newton observations of the galaxy cluster Abell 514. This cluster shows a very complex X-ray morphology. Radio observations show that there are six radio sources located inside the cluster. This makes it possible to determine the magnetic field strength using the Faraday rotation method. This cluster is an example for the hierarchical growth of structure and a very interesting object for studying the correlation between magnetic field strength and X-ray properties.

scholarly journals Properties of the Medium Causing Asymmetric Depolarization in Strong Double Radio Sources with One Jet

1990 ◽  
Vol 140 ◽  
pp. 482-482
Author(s):  
A. Crusius-Wätzel ◽  
P.L. Biermann ◽  
I. Lerche ◽  
R. Schlickeiser
Keyword(s):  
Magnetic Field ◽  
Faraday Rotation ◽  
Magnetized Plasma ◽  
Radio Sources ◽  
Radio Waves ◽  
X Ray ◽  
Hot Gas ◽  
Radio Lobe ◽  
The One ◽  
The Magnetic Field

Polarization data of strong double-lobed radio sources (Garrington et al., 1988a; Laing, 1988) in many cases show that one side is more depolarized than the other. Since a jet is seen only on the less depolarized side it can be concluded that this radio lobe is nearer to us, if the one-sidedness of the jet is interpreted by bulk relativistic motion. The effect is then due to random Faraday rotation where the RMS-rotation angle is larger than about π/2 for the longer wavelength. This suggests an intervening magnetized plasma which may be the hot gas in the halos of the (elliptical) galaxies or in the cluster. Comparing the effects of both, the intracluster medium (ICM) probably is the dominating component. Garrington (1988b) comes to the same conclusion. Considering the transport of polarized radio waves in a turbulent Faraday screen (cells of size l0) we further find that the coherence length of the magnetic field is of the order of l0 = 1–4 kpc. From EINSTEIN X-ray data (for 3C9, 4C01.11, 3C270.1, 3C275.1, 3C208) we find luminosities in the range Lx = 0.6–7 × 1045erg s−1, which can only be due to the cluster gas or an active galactic nucleus. If we assume that the total X-ray flux is produced by the ICM the electron core densities are n0 = 2–7 × 10−3 cm−3. Combining this with the values for l0 gives upper limits to the ratio of thermal to magnetic pressure (plasma-beta) of βp = 50–370 and lower limits to the core magnetic field strength of B0 = 3–9 μG. If the AGN contributes substantially to the X-ray emission the given limits would be even stronger, in the direction of equipartition of energy in the hot gas and in the magnetic field, since B0 has to be larger if n0 is smaller to account for the same dispersion in Faraday rotation. We plan to separate the diffuse and the pointlike emission by ROSAT observations. A more detailed version of this paper will be presented elsewhere (Crusius–Wätzel et al., 1989).

scholarly journals Relating magnetic field strengths to hard X-ray emission in solar flares

2004 ◽  
Vol 423 (1) ◽  
pp. 363-372 ◽  
Author(s):  
C. P. Goff ◽  
S. A. Matthews ◽  
L. van Driel-Gesztelyi ◽  
L. K. Harra
Keyword(s):  
Magnetic Field ◽  
Solar Flares ◽  
X Ray ◽  
Field Strengths

scholarly journals Magnetic Field Strengths in the Hot Spots and Lobes of Three Powerful Fanaroff‐Riley Type II Radio Sources

2002 ◽  
Vol 581 (2) ◽  
pp. 948-973 ◽  
Author(s):  
M. J. Hardcastle ◽  
M. Birkinshaw ◽  
R. A. Cameron ◽  
D. E. Harris ◽  
L. W. Looney ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Hot Spots ◽  
Radio Sources ◽  
Type Ii ◽  
Field Strengths

Magnetic-field strengths from optical polarization data

1967 ◽  
Vol 31 ◽  
pp. 381-383
Author(s):  
J. M. Greenberg
Keyword(s):  
Magnetic Field ◽  
Optical Polarization ◽  
Polarization Data ◽  
Term Model ◽  
Source Of Information ◽  
Field Strengths

Van de Hulst (Paper 64, Table 1) has marked optical polarization as a questionable or marginal source of information concerning magnetic field strengths. Rather than arguing about this–I should rate this method asq+-, or quarrelling about the term ‘model-sensitive results’, I wish to stress the historical point that as recently as two years ago there were still some who questioned that optical polarization was definitely due to magnetically-oriented interstellar particles.

Sign in / Sign up

Export Citation Format

Share Document