Spectral index of synchrotron emission: insights from the diffuse and magnetised interstellar medium

1998 ◽

Vol 184 ◽

pp. 351-352 ◽

Cited By ~ 1

Author(s):

P. Hoernes ◽

R. Beck ◽

E.M. Berkhuijsen

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Spectral Index ◽

Central Region ◽

Relativistic Electrons ◽

Synchrotron Emission ◽

The Magnetic Field

At the centre of M31 the nonthermal spectral index between λ20 cm and λ6 cm is −0.2. It slowly decreases along the southern arm and the northern filaments visible in Hα, but perpendicular to these features it increases much faster. The magnetic field runs along the arm and the filaments. These phenomena suggest the existence of a mono-energetic source of relativistic electrons in the nucleus.

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SPATIAL VARIATIONS IN THE SPECTRAL INDEX OF POLARIZED SYNCHROTRON EMISSION IN THE 9 yrWMAPSKY MAPS

The Astrophysical Journal ◽

10.1088/0004-637x/790/2/104 ◽

2014 ◽

Vol 790 (2) ◽

pp. 104 ◽

Cited By ~ 38

Author(s):

U. Fuskeland ◽

I. K. Wehus ◽

H. K. Eriksen ◽

S. K. Næss

Keyword(s):

Spectral Index ◽

Spatial Variations ◽

Synchrotron Emission

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Radio emission from accreting isolated black holes in our galaxy

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1809 ◽

2019 ◽

Vol 488 (2) ◽

pp. 2099-2107 ◽

Cited By ~ 2

Author(s):

Daichi Tsuna ◽

Norita Kawanaka

Keyword(s):

Black Holes ◽

Radio Emission ◽

Interstellar Medium ◽

Binary Systems ◽

Electron Acceleration ◽

Stellar Mass ◽

Synchrotron Emission ◽

Accelerated Electrons ◽

Accretion Flow

ABSTRACT Apart from the few tens of stellar-mass black holes discovered in binary systems, an order of 108 isolated black holes (IBHs) are believed to be lurking in our Galaxy. Although some IBHs are able to accrete matter from the interstellar medium, the accretion flow is usually weak and thus radiatively inefficient, which results in significant material outflow. We study electron acceleration generated by the shock formed between this outflow and the surrounding material, and the subsequent radio synchrotron emission from accelerated electrons. By numerically calculating orbits of IBHs to obtain their spatial and velocity distributions, we estimate the number of IBHs detectable by surveys using SKA1-mid (SKA2) as ∼30 (∼700) for the most optimistic case. The SKA’s parallax measurements may accurately give their distances, possibly shedding light on the properties of the black holes in our Galaxy.

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The discovery of radio halos in the frontier fields clusters Abell S1063 and Abell 370

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936953 ◽

2020 ◽

Vol 636 ◽

pp. A3 ◽

Cited By ~ 3

Author(s):

C. Xie ◽

R. J. van Weeren ◽

L. Lovisari ◽

F. Andrade-Santos ◽

A. Botteon ◽

...

Keyword(s):

Spectral Index ◽

Relativistic Electrons ◽

Synchrotron Emission ◽

Scaling Relation ◽

Diffuse Emission ◽

Very Large Array ◽

X Ray ◽

Radio Halo ◽

Radio Power ◽

Radio Halos

Context. Massive merging galaxy clusters often host diffuse megaparsec-scale radio synchrotron emission. This emission originates from relativistic electrons in the ionized intracluster medium. An important question is how these synchrotron emitting relativistic electrons are accelerated. Aims. Our aim is to search for diffuse emission in the Frontier Fields clusters Abell S1063 and Abell 370 and characterize its properties. While these clusters are very massive and well studied at some other wavelengths, no diffuse emission has been reported for these clusters so far. Methods. We obtained 325 MHz Giant Metrewave Radio Telescope (GMRT) and 1–4 GHz Jansky Very Large Array (VLA) observations of Abell S1063 and Abell 370. We complement these data with Chandra and XMM-Newton X-ray observations. Results. In our sensitive images, we discover radio halos in both clusters. In Abell S1063, a giant radio halo is found with a size of ∼1.2 Mpc. The integrated spectral index between 325 MHz and 1.5 GHz is −0.94 ± 0.08 and it steepens to −1.77 ± 0.20 between 1.5 and 3.0 GHz. This spectral steepening provides support for the turbulent reacceleration model for radio halo formation. Abell 370 hosts a faint radio halo mostly centered on the southern part of this binary merging cluster, with a size of ∼500−700 kpc. The spectral index between 325 MHz and 1.5 GHz is −1.10 ± 0.09. Both radio halos follow the known scaling relation between the cluster mass proxy Y500 and radio power, which is consistent with the idea that they are related to ongoing cluster merger events.

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Synchrotron Emission as a Tracer of the Outflow in M82

Symposium - International Astronomical Union ◽

10.1017/s0074180900089178 ◽

1991 ◽

Vol 144 ◽

pp. 281-285

Author(s):

E.R. Seaquist ◽

Nils Odegard

Keyword(s):

Spectral Index ◽

Synchrotron Emission ◽

Physical Processes ◽

Index Distribution

We report the discovery of radio synchrotron emission from the outflow in M82. The brightness morphology and radio spectral index distribution add new insights into the physical processes and origin of the wind, which are briefly discussed in this paper.

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