2011A&A...530A..24B

Query : 2011A&A...530A..24B

2011A&A...530A..24B - Astronomy and Astrophysics, volume 530A, 24-24 (2011/6-1)

Fractional polarization as a probe of magnetic fields in the intra-cluster medium.

BONAFEDE A., GOVONI F., FERETTI L., MURGIA M., GIOVANNINI G. and BRUEGGEN M.

Abstract (from CDS):

It is now established that magnetic fields are present in the intra-cluster medium (ICM) of galaxy clusters, as revealed by observations of radio halos and radio relics and from the study of the Faraday rotation measures of sources located either behind or within clusters. Deep radio polarization observations of clusters have been performed in the last years, and the properties of the ICM magnetic field have been constrained in a small number of well-studied objects. The aim of this work is to investigate the average properties of the ICM magnetic fields, and to search for possible correlations with the ICM thermal properties and cluster radio emission. We have selected a sample of 39 massive galaxy clusters from the HIghest X-ray FLUx Galaxy Cluster Sample, and used Northern VLA Sky Survey data to analyze the fractional polarization of radio sources out to 10 core radii from the cluster centers. We have investigated how different magnetic field strengths affect the observed polarized emission of sources lying at different projected distances from the cluster center. In addition, statistical tests are performed to investigate the fractional polarization trends in clusters with different thermal and non-thermal properties. We find a trend of the fractional polarization with the cluster impact parameter, with fractional polarization increasing at the cluster periphery and decreasing toward the cluster center. Such trend can be reproduced by a magnetic field model with central value of few µG. The logrank statistical test indicates that there are no differences in the depolarization trend observed in cluster with and without radio halo, while the same test indicates significant differences when the depolarization trend of sources in clusters with and without cool core are compared. The comparison between clusters with high and low temperatures does not yields significant differences. Although the role of the gas density should be better accounted for, these results give important indications for models that require a role of the ICM magnetic field to explain the presence of cool core and radio halos in galaxy clusters.

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Journal keyword(s): magnetic fields - radiation mechanisms: non-thermal - polarization - galaxies: clusters: intracluster medium - methods: observational - galaxies: clusters: general

Simbad objects: 44

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Number of rows : 44
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 ACO 85 ClG 00 41 36.21 -09 19 30.4           ~ 909 0
2 ACO 119 ClG 00 56 08.57 -01 12 00.8           ~ 555 2
3 ACO 133 ClG 01 02 41.5 -21 52 53           ~ 368 1
4 ClG 0217+70 ClG 02 17 00.0 +70 36 00           ~ 31 0
5 ACO 399 ClG 02 57 56.4 +13 00 59           ~ 396 0
6 ACO 401 ClG 02 58 56.9 +13 34 56           ~ 566 0
7 ACO 3112 ClG 03 17 52.4 -44 14 35           ~ 311 1
8 ZwCl 0335+0956 ClG 03 38 35.3 +09 57 54           ~ 383 1
9 ACO 3158 ClG 03 42 39.6 -53 37 50           ~ 304 0
10 ACO 478 ClG 04 13 20.7 +10 28 35           ~ 502 0
11 ACO 3266 ClG 04 31 11.9 -61 24 23           ~ 410 0
12 ACO 496 ClG 04 33 38.8 -13 15 59           ~ 694 2
13 ACO 3391 ClG 06 26 15.4 -53 40 52           ~ 202 1
14 ClG J0717+3745 ClG 07 17 36.50 +37 45 23.0           ~ 463 0
15 B3 0714+378 Rad 07 17 36.6 +37 45 01           ~ 170 2
16 ACO 665 ClG 08 30 45.2 +65 52 55           ~ 437 0
17 ACO 754 ClG 09 09 08.4 -09 39 58           ~ 666 1
18 ACO 1213 ClG 11 16 26.98 +29 16 23.9           ~ 151 0
19 ZwCl 1215+0400 ClG 12 17 43.62 +03 38 51.5           ~ 153 0
20 M 84 Sy2 12 25 03.74333 +12 53 13.1393 12.67 12.09 10.49     ~ 1762 2
21 ACO 1644 ClG 12 57 11.6 -17 24 34           ~ 366 1
22 ACO 1650 ClG 12 58 42.0 -01 45 45           ~ 304 0
23 ACO 1651 ClG 12 59 22.43 -04 11 47.1           ~ 290 0
24 ACO 1656 ClG 12 59 44.40 +27 54 44.9           ~ 4796 2
25 ACO 1736 ClG 13 26 52.1 -27 06 33           ~ 249 2
26 ACO 3558 ClG 13 27 54.8 -31 29 32           ~ 442 2
27 ACO 3562 ClG 13 33 31.8 -31 40 23           ~ 314 1
28 ACO 3571 ClG 13 47 28.9 -32 51 57           ~ 284 2
29 ACO 1795 ClG 13 48 50.48 +26 35 07.4           ~ 1266 0
30 ACO 2029 ClG 15 10 56.2 +05 44 42           ~ 943 0
31 ACT-CL J1521.8+0742 ClG 15 21 55.14 +07 41 27.2     15.13     ~ 311 0
32 ACO 2065 ClG 15 22 29.3 +27 42 22           ~ 374 0
33 ACO 2142 ClG 15 58 14.38 +27 12 57.8           ~ 768 0
34 ACO 2147 ClG 16 02 11.96 +15 55 11.5           ~ 403 0
35 ACO 2163 ClG 16 15 46.1 -06 08 50           ~ 562 0
36 ACO 2199 ClG 16 28 43.31 +39 34 07.6           ~ 1171 1
37 ACO 2204 ClG 16 32 45.7 +05 34 43           ~ 436 0
38 ACO 2244 ClG 17 02 40.33 +34 02 58.7           ~ 281 0
39 ACO 2256 ClG 17 03 09.4 +78 39 36           ~ 885 1
40 ACO 2255 ClG 17 12 50.04 +64 03 10.6           ~ 568 0
41 ACO 3667 ClG 20 12 33.68 -56 50 26.3           ~ 627 1
42 ACO S 1101 ClG 23 13 58.5 -42 43 39           ~ 258 1
43 ACO 2597 ClG 23 25 19.70 -12 07 27.7           ~ 539 0
44 ACO 4059 ClG 23 57 02.2 -34 45 58           ~ 380 1

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