2017A&A...603A.125V


Query : 2017A&A...603A.125V

2017A&A...603A.125V - Astronomy and Astrophysics, volume 603A, 125-125 (2017/7-1)

The two-component giant radio halo in the galaxy cluster Abell 2142.

VENTURI T., ROSSETTI M., BRUNETTI G., FARNSWORTH D., GASTALDELLO F., GIACINTUCCI S., LAL D.V., RUDNICK L., SHIMWELL T.W., ECKERT D., MOLENDI S. and OWERS M.

Abstract (from CDS):

Aims. We report on a spectral study at radio frequencies of the giant radio halo in A 2142 (z=0.0909), which we performed to explore its nature and origin. The optical and X-ray properties of the cluster suggest that A 2142 is not a major merger and the presence of a giant radio halo is somewhat surprising.
Methods. We performed deep radio observations of A 2142 with the Giant Metrewave Radio Telescope (GMRT) at 608MHz, 322MHz, and 234MHz and with the Very Large Array (VLA) in the 1-2GHz band. We obtained high-quality images at all frequencies in a wide range of resolutions, from the galaxy scale, i.e. ∼5'', up to ∼60'' to image the diffuse cluster-scale emission. The radio halo is well detected at all frequencies and extends out to the most distant cold front in A 2142, about 1 Mpc away from the cluster centre. We studied the spectral index in two regions: the central part of the halo, where the X-ray emission peaks and the two brightest dominant galaxies are located; and a second region, known as the ridge (in the direction of the most distant south-eastern cold front), selected to follow the bright part of the halo and X-ray emission. We complemented our deep observations with a preliminary LOw Frequency ARray (LOFAR) image at 118MHz and with the re-analysis of archival VLA data at 1.4GHz.
Results. The two components of the radio halo show different observational properties. The central brightest part has higher surface brightess and a spectrum whose steepness is similar to those of the known radio halos, i.e. α1.78GHz118MHz=1.33±0.08 . The ridge, which fades into the larger scale emission, is broader in size and has considerably lower surface brightess and a moderately steeper spectrum, i.e. α1.78GHz118MHz∼1.5. We propose that the brightest part of the radio halo is powered by the central sloshing in A 2142, in a process similar to what has been suggested for mini-halos, or by secondary electrons generated by hadronic collisions in the ICM. On the other hand, the steeper ridge may probe particle re-acceleration by turbulence generated either by stirring the gas and magnetic fields on a larger scale or by less energetic mechanisms, such as continuous infall of galaxy groups or an off-axis (minor) merger.

Abstract Copyright: © ESO, 2017

Journal keyword(s): galaxies: clusters: general - galaxies: clusters: individual: A 2142 - radio continuum: general - radio continuum: general

Nomenclature: Table A.1 and Fig. A.1: [VRB2017] NN (Nos 1-42) = [VRB2017] GMRT JHHMMSS+DDMMSS N=42.

Status at CDS : All or part of tables of objects could be ingested in SIMBAD with priority 2.

Simbad objects: 12

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Number of rows : 12
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 3C 48 QSO 01 37 41.2996631208 +33 09 35.080388820   16.62 16.20     ~ 2820 2
2 ACO 426 ClG 03 19 47.2 +41 30 47           ~ 2269 1
3 ACO 521 ClG 04 54 08.6 -10 14 39           ~ 250 0
4 3C 286 Sy1 13 31 08.2883506368 +30 30 32.960091564   17.51 17.25     ~ 4351 2
5 B2 1556+27 GiC 15 58 14.0 +27 16 22           ~ 11 2
6 ACO 2142 ClG 15 58 14.38 +27 12 57.8           ~ 770 0
7 2MASX J15582091+2720010 BiC 15 58 20.8826270472 +27 20 01.464333504   16.07       ~ 17 0
8 ICRF J160913.3+264129 Sy2 16 09 13.3196 +26 41 29.042   19       ~ 238 0
9 ACO 2261 ClG 17 22 26.9 +32 07 58           ~ 343 0
10 ClG 1821+64 ClG 18 21 56.7276 +64 20 55.841           ~ 505 1
11 ACO 2319 ClG 19 20 45.3 +43 57 43           ~ 462 1
12 ACO 2390 ClG 21 53 37.4 +17 41 46           ~ 689 2

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