Electron Energy Spectrum of the West Lobe of Fornax A from a Hard X-ray Observation with Suzaku

摘要

Suzaku Hard X-ray observation of the archetypical X-ray emitting radio lobe object Fornax A (NGC 1316) is reported. The results firstly revealed a non-thermal X-ray spectrum up to 20 keV from the lobe, and showed that a single component of non-relativistic electron with an energy distribution over a two order of magnitudes generates both the X-ray and radio emissions. On the basis of observations made with Suzaku, the present paper shows that a 0.7 - 20 keV spectrum is well described by a single power-law model with an energy index of 0.68 and a flux density of 0.12 ± 0.01 nJy at 1 keV from the West lobe. Utilizing published radio data, the multiwavelength spectrum shows an undoubtable single electron energy, distribution over a Lorentz factor γ = 300 — 90000, generating both the X-ray and radio emissions.