2020A&A...636A..30R


C.D.S. - SIMBAD4 rel 1.7 - 2021.01.27CET11:44:52

2020A&A...636A..30R - Astronomy and Astrophysics, volume 636A, 30-30 (2020/4-1)

New mysteries and challenges from the Toothbrush relic: wideband observations from 550 MHz to 8 GHz.

RAJPUROHIT K., HOEFT M., VAZZA F., RUDNICK L., VAN WEEREN R.J., WITTOR D., DRABENT A., BRIENZA M., BONNASSIEUX E., LOCATELLI N., KALE R. and DUMBA C.

Abstract (from CDS):


Context. Radio relics are diffuse extended synchrotron sources that originate from shock fronts induced by galaxy cluster mergers. The particle acceleration mechanism at the shock fronts is still under debate. The galaxy cluster 1RXS J0603.3+4214 hosts one of the most intriguing examples of radio relics, known as the Toothbrush.
Aims. In order to understand the mechanism(s) that accelerate(s) relativistic particles in the intracluster medium, we investigated the spectral properties of large-scale diffuse extended sources in the merging galaxy cluster 1RXS J0603.3+4214.
Methods. We present new wideband radio continuum observations made with uGMRT and VLA. Our new observations, in combination with previously published data, allowed us to carry out a detailed high-spatial-resolution spectral and curvature analysis over a wide range of frequencies.
Results. The integrated spectrum of the Toothbrush closely follows a power law over almost two orders of magnitude in frequency, with a spectral index of -1.16±0.02. We do not find any evidence of spectral steepening below 8GHz. The subregions of the Toothbrush also exhibit near-perfect power laws and identical spectral slopes, suggesting that the observed spectral index is rather set by the distribution of Mach numbers which may have a similar shape at different parts of the shock front. Indeed, numerical simulations show an intriguing similar spectral index, indicating that the radio spectrum is dominated by the average over the inhomogeneities within the shock, with most of the emission coming from the tail of the Mach number distribution. In contrast to the Toothbrush, the spectra of the fainter relics show a high-frequency steepening. Moreover, the integrated spectrum of the halo also follows a power law from 150MHz to 3GHz with a spectral index of -1.16±0.04. We do not find any evidence for spectral curvature, not even in subareas of the halo. This suggest a homogeneous acceleration throughout the cluster volume. Between the "brush" region of the Toothbrush and the halo, the color-color analysis reveals emission that was consistent with an overlap between the two different spectral regions.
Conclusions. None of the relic structures, that is, the Toothbrush as a whole or its subregions or the other two fainter relics, show spectral shapes consistent with a single injection of relativistic electrons, such as at a shock, followed by synchrotron aging in a relatively homogeneous environment. Inhomogeneities in some combination of Mach number, magnetic field strength, and projection effects dominate the observed spectral shapes.

Abstract Copyright: © ESO 2020

Journal keyword(s): galaxies: clusters: individual: 1RXS J0603.3+4214 - galaxies: clusters: intracluster medium - large-scale structure of Universe - acceleration of particles - radiation mechanisms: non-thermal - shock waves

Simbad objects: 9

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Number of rows : 9

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 3C 48 QSO 01 37 41.2995845985 +33 09 35.079126038   16.62 16.20     ~ 2550 2
2 3C 84 Sy2 03 19 48.1597607660 +41 30 42.114155434   13.10 12.48 11.09   ~ 3603 3
3 ICRF J052109.8+163822 Sy1 05 21 09.88592749 +16 38 22.0517668   19.37 18.84 18.480   ~ 764 1
4 ICRF J054236.1+495107 Sy1 05 42 36.13789843 +49 51 07.2337251   18.45 17.80 17.210   ~ 1295 1
5 7C 055201.39+394824.00 QSO 05 55 30.80561150 +39 48 49.1649664     18.0 17.5   ~ 472 2
6 ClG J0603.3+4214 ClG 06 03.3 +42 14           ~ 74 0
7 1RXS J060313.4+421231 ClG 06 03 21.4664 +42 13 56.245           ~ 16 0
8 3C 286 Sy1 13 31 08.2885060664 +30 30 32.960825108   17.51 17.25     ~ 3817 2
9 QSO B1404+286 BLL 14 07 00.3933203928 +28 27 14.695133019   16.13 15.35 10.29   ~ 691 2

    Equat.    Gal    SGal    Ecl

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2021.01.27-11:44:52

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