The structure of the radio halo

Author(s):  
Frazer Owen
Keyword(s):  

2018 ◽  
Vol 14 (S344) ◽  
pp. 255-258
Author(s):  
Volker Heesen ◽  
Aritra Basu ◽  
Elias Brinks ◽  
George Heald ◽  
Andrew Fletcher ◽  
...  

AbstractLow-mass dwarf irregular galaxies are subject to outflows, in which cosmic rays may play a very important role; they can be traced via their electron component, the cosmic ray electrons (CRe), in the radio continuum as non-thermal synchrotron emission. With the advent of sensitive low-frequency observations, such as with the Low-Frequency Array (LOFAR), we can trace CRe far away from star formation sites. Together with GHz-observations, such as with the Very Large Array (VLA), we can study spatially resolved radio continuum spectra at matched angular resolution and sensitivity. Here, we present results from our 6-GHz VLA survey of 40 nearby dwarf galaxies and our LOFAR study of the nearby starburst dwarf irregular galaxy IC 10. We explore the relation of RC emission with star formation tracers and study in IC 10 the nature of a low-frequency radio halo, which we find to be the result of a galactic wind.



2013 ◽  
Vol 557 ◽  
pp. A99 ◽  
Author(s):  
R. Kale ◽  
T. Venturi ◽  
S. Giacintucci ◽  
D. Dallacasa ◽  
R. Cassano ◽  
...  
Keyword(s):  


1991 ◽  
Vol 144 ◽  
pp. 267-280 ◽  
Author(s):  
Rainer Beck

Spiral galaxies host interstellar magnetic fields of 4-15 μG total strength. A significant fraction of the field lines shows large-scale structures. At face-on or moderately inclined view, the field lines run generally parallel to the spiral arms, either with uniform direction with respect to azimuthal angle (axisymmetric spiral, ASS), with one reversal along azimuthal angle (bisymmetric spiral, BSS), or with spiral orientation without dominating direction.At edge-on view, the field is concentrated in a thin disk, often surrounded by a thick radio disk with field lines mostly parallel to the plane, similar to the quadrupole-type dynamo field. Radio polarization data from NGC891 indicate that the thermal gas seen in Hα is responsible for Faraday depolarization. The required scaleheight of the field of ~4 kpc is comparable to the value expected in case of energy equipartition between magnetic fields and cosmic rays. The interacting edge-on galaxy NGC 4631 shows a much larger radio halo with field lines perpendicular to the disk, possibly driven by a strong galactic wind or the result of a dipole-type halo field.Field lines bending out of the plane are also visible in face-on galaxies as regions with high rotation measures and low star-formation activity. The resemblance to the phenomenon of the solar corona suggests to call them “galactic coronal holes”.



2007 ◽  
Vol 467 (1) ◽  
pp. 37-48 ◽  
Author(s):  
R. Barrena ◽  
W. Boschin ◽  
M. Girardi ◽  
M. Spolaor
Keyword(s):  


2014 ◽  
Vol 781 (2) ◽  
pp. L32 ◽  
Author(s):  
R. J. van Weeren ◽  
H. T. Intema ◽  
D. V. Lal ◽  
A. Bonafede ◽  
C. Jones ◽  
...  
Keyword(s):  


1985 ◽  
Vol 106 ◽  
pp. 245-246
Author(s):  
Jelena Milogradov-Tuin

The distribution of total spectral indices between 38 and 408 MHz with a resolution of for δ>-25° has the following main properties:1. Relatively small variations of spectral indices over the sky.2. High indices in the central region at high galactic latitudes.3. Moderately low spectral indices in the anticentre region.4. Lower indices in the low-brightness regions (cold holes).5. The lowest indices in regions containing large amounts of HII.



1990 ◽  
Vol 105 (8-9) ◽  
pp. 845-856
Author(s):  
Kwang-Tae Kim


1997 ◽  
Vol 113 ◽  
pp. 2006 ◽  
Author(s):  
Jayanne English ◽  
Judith A. Irwin
Keyword(s):  


1983 ◽  
Vol 270 ◽  
pp. 410 ◽  
Author(s):  
G. Gavazzi ◽  
G. Trinchieri
Keyword(s):  
X Ray ◽  


2020 ◽  
Vol 492 (2) ◽  
pp. 2405-2417 ◽  
Author(s):  
W Boschin ◽  
M Girardi ◽  
F Gastaldello

ABSTRACT We present the study of the internal dynamics of the intriguing galaxy cluster Abell 1703, a system hosting a probable giant radio halo whose dynamical status is still controversial. Our analysis is based on unpublished spectroscopic data acquired at the Italian Telescopio Nazionale Galileo and data publicly available in the literature. We also use photometric data from the Sloan Digital Sky Survey. We select 147 cluster members and compute the cluster redshift 〈z〉 ∼ 0.277 and the global line-of-sight velocity dispersion σv ∼ 1300 km s−1. We infer that Abell 1703 is a massive cluster: M200 ∼ 1–2 × 1015 M⊙. The results of our study disagree with the picture of an unimodal, relaxed cluster as suggested by previous studies based on the gravitational lensing analysis and support the view of a perturbed dynamics proposed by recent works based on Chandra X-ray data. The first strong evidence of a dynamically disturbed cluster comes from the peculiarity of the BCG velocity with respect to the first moment of the velocity distribution of member galaxies. Moreover, several statistical tests employed to study the cluster galaxies kinematics find significant evidence of substructure, being Abell 1703 composed by at least two or three subclumps probably caught after the core–core passage. In this observational scenario, the suspected existence of a radio halo in the centre of this cluster is not surprising and well agrees with the theoretical models describing diffuse radio sources in clusters.



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