The Suzaku observation of a giant radio galaxy 3C 35 revealed faint extended X-ray emission , associated with its radio lobes and/or host galaxy .
After careful subtraction of the X-ray and non-X-ray background and contaminating X-ray sources , the X-ray spectrum of the faint emission was reproduced by a sum of the power-law ( PL ) and soft thermal components .
The soft component was attributed to the thermal plasma emission from the host galaxy .
The photon index of the PL component , \Gamma = 1.35 _ { -0.86 } ^ { +0.56 } _ { -0.10 } ^ { +0.11 } where the first and second errors represent the statistical and systematic ones , was found to agree with the synchrotron radio index from the lobes , \Gamma _ { R } = 1.7 .
Thus , the PL component was attributed to the inverse Compton ( IC ) X-rays from the synchrotron electrons in the lobes .
The X-ray flux density at 1 keV was derived as 13.6 \pm 5.4 _ { -3.6 } ^ { +4.0 } nJy with the photon index fixed at the radio value .
The X-ray surface brightness from these lobes ( \sim 0.2 nJy arcmin ^ { -2 } ) is lowest among the lobes studied through the IC X-ray emission .
In combination with the synchrotron radio flux density , 7.5 \pm 0.2 Jy at 327.4 MHz , the electron energy density spatially averaged over the lobes was evaluated to be the lowest among those radio galaxies , as u _ { e } = ( 5.8 \pm 2.3 _ { -1.7 } ^ { +1.9 } ) \times 10 ^ { -14 } ergs cm ^ { -3 } over the electron Lorentz factor of 10 ^ { 3 } – 10 ^ { 5 } .
The magnetic energy density was calculated as u _ { m } = ( 3.1 _ { -1.0 } ^ { +2.5 } _ { -0.9 } ^ { +1.4 } ) \times 10 ^ { -14 } ergs cm ^ { -3 } , corresponding to the magnetic field strength of 0.88 _ { -0.16 } ^ { +0.31 } _ { -0.14 } ^ { +0.19 } \mu G. These results suggest that the energetics in the 3C 35 lobes are nearly consistent with equipartition between the electrons and magnetic fields .