2004A&A...413...17P


Query : 2004A&A...413...17P

2004A&A...413...17P - Astronomy and Astrophysics, volume 413, 17-36 (2004/1-1)

Constraining the population of cosmic ray protons in cooling flow clusters with γ-ray and radio observations: Are radio mini-halos of hadronic origin?

PFROMMER C. and ENSSLIN T.A.

Abstract (from CDS):

We wish to constrain the cosmic-ray proton (CRp) population in galaxy clusters. By hadronic interactions with the thermal gas of the intra-cluster medium (ICM), the CRp produce γ-rays for which we develop an analytic formalism to deduce their spectral distribution. Assuming the CRp-to-thermal energy density ratio XCRp and the CRp spectral index to be spatially constant, we derive an analytic relation between the γ-ray and bolometric X-ray fluxes, Fγ and FX. Based on our relation, we compile a sample of suitable clusters which are promising candidates for future detection of γ-rays resulting from hadronic CRp interactions. Comparing to EGRET upper limits, we constrain the CRp population in the cooling flow clusters Perseus and Virgo to XCRp<20%. Assuming a plausible value for the CRp diffusion coefficient κ, we find the central CRp injection luminosity of M 87 to be limited to 1043erg/sκ/(1029cm2/s). The synchrotron emission from secondary electrons generated in CRp hadronic interactions allows even tighter limits to be placed on the CRp population using radio observations. We obtain excellent agreement between the observed and theoretical radio brightness profiles for Perseus, but not for Coma without a radially increasing CRp-to-thermal energy density profile. Since the CRp and magnetic energy densities necessary to reproduce the observed radio flux are very plausible, we propose synchrotron emission from secondary electrons as an attractive explanation of the radio mini-halos found in cooling flow clusters. This model can be tested with future sensitive γ-ray observations of the accompanying π0-decays. We identify Perseus (A 426), Virgo, Ophiuchus, and Coma (A 1656) as the most promising candidate clusters for such observations.

Abstract Copyright:

Journal keyword(s): galaxies: cooling flows - galaxies: cluster: general - galaxies: cluster: individual: Perseus (A426) - galaxies: intergalactic medium - ISM: cosmic rays - radiation mechanisms: non-thermal

Errata: erratum vol. 426, p. 777 (2004)

Simbad objects: 14

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Number of rows : 14
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 ACO 85 ClG 00 41 37.8 -09 20 33           ~ 848 0
2 ACO 426 ClG 03 19 47.2 +41 30 47           ~ 2138 1
3 3C 84 Sy2 03 19 48.1599902040 +41 30 42.108850836   13.10 12.48 11.09   ~ 3835 3
4 NAME Virgo Cluster ClG 12 26 32.1 +12 43 24           ~ 6345 0
5 M 87 AGN 12 30 49.42338414 +12 23 28.0436859 10.16 9.59 8.63   7.49 ~ 6784 3
6 ACO 3526 ClG 12 48 51.8 -41 18 21           ~ 1031 2
7 ACO 1656 ClG 12 59 48.7 +27 58 50           ~ 4575 2
8 ACO 3571 ClG 13 47 28.9 -32 51 57           ~ 272 2
9 ACO 2199 ClG 16 28 37.0 +39 31 28           ~ 1134 1
10 NAME Triangulum Australis Cluster ClG 16 38 16.1 -64 20 50           ~ 110 0
11 ACO 2256 ClG 17 03 43.5 +78 43 03           ~ 862 1
12 NAME Oph Cluster ClG 17 12 24.7 -23 21 01           ~ 260 0
13 ACO 2319 ClG 19 20 45.3 +43 57 43           ~ 440 1
14 ACO 3667 ClG 20 12 33.68 -56 50 26.3           ~ 599 1

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2022.12.05-15:42:38

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