TY - JOUR
T1 - Non-thermal emission in radio galaxy lobes - II. Centaurus A, Centaurus B, and NGC 6251
AU - Persic, Massimo
AU - Rephaeli, Yoel
N1 - Publisher Copyright:
© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
PY - 2019/12/1
Y1 - 2019/12/1
N2 - Radio and γ -ray measurements of large lobes of several radio galaxies provide adequate basis for determining whether emission in these widely separated spectral regions is largely by energetic electrons. This is very much of interest as there is of yet no unequivocal evidence for a significant energetic proton component to account for γ -ray emission by neutral pion decay. A quantitative assessment of the pion yield spectral distribution necessitates full accounting of the local and background radiation fields in the lobes; indeed, doing so in our recent analysis of the spectral energy distribution of the Fornax A lobes considerably weakened previous conclusions on the hadronic origin of the emission measured by the Fermi satellite. We present the results of similar analyses of the measured radio, X-ray, and γ -ray emission from the lobes of Centaurus A, Centaurus B, and NGC 6251. The results indicate that the measured γ -ray emission from these lobes can be accounted for by Compton scattering of the radio-emitting electrons off the superposed radiation fields in the lobes; consequently, we set upper bounds on the energetic proton contents of the lobes.
AB - Radio and γ -ray measurements of large lobes of several radio galaxies provide adequate basis for determining whether emission in these widely separated spectral regions is largely by energetic electrons. This is very much of interest as there is of yet no unequivocal evidence for a significant energetic proton component to account for γ -ray emission by neutral pion decay. A quantitative assessment of the pion yield spectral distribution necessitates full accounting of the local and background radiation fields in the lobes; indeed, doing so in our recent analysis of the spectral energy distribution of the Fornax A lobes considerably weakened previous conclusions on the hadronic origin of the emission measured by the Fermi satellite. We present the results of similar analyses of the measured radio, X-ray, and γ -ray emission from the lobes of Centaurus A, Centaurus B, and NGC 6251. The results indicate that the measured γ -ray emission from these lobes can be accounted for by Compton scattering of the radio-emitting electrons off the superposed radiation fields in the lobes; consequently, we set upper bounds on the energetic proton contents of the lobes.
KW - Galaxies: active
KW - Galaxies: cosmic rays
KW - Galaxies: individual: Centaurus A
KW - Galaxies: individual: Centaurus B
KW - Galaxies: individual: NGC 6251
KW - Gamma rays: galaxies
KW - Radiation mechanisms: non-thermal
UR - http://www.scopus.com/inward/record.url?scp=85079630556&partnerID=8YFLogxK
U2 - 10.1093/mnras/stz2527
DO - 10.1093/mnras/stz2527
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AN - SCOPUS:85079630556
SN - 0035-8711
VL - 490
SP - 1489
EP - 1497
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 2
ER -