X-ray measurements of the field and particle energy distributions in the west lobe of the radio galaxy NGC 1316 (Fornax A)

M. Tashiro, K. Makishima, Naoko Iyomoto, N. Isobe, H. Kaneda

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Abstract

A follow-up X-ray study was made of the west lobe of the radio galaxy Fornax A (NGC 1316) that was based on new ASCA observations made in 1997 for 98 ks and that incorporated the previous observation in 1994 for 39 ks. The 0.7-10 keV spectrum of the emission can be described by a power law with an energy index of 0.74 ± 0.10, which agrees with the synchrotron radio index of 0.9 ± 0.2. Therefore, the X-rays are reconfirmed to arise via the inverse Compton scattering of the cosmic microwave photons, as Kaneda et al. and Feigelson et al. concluded. The surface brightness of the inverse Compton X-rays exhibits a relatively flat distribution over the west lobe, indicative of an approximately spherical emissivity distribution with a radius of ∼11′ (75 kpc). In contrast, the 1.4 GHz radio image by Ekers et al. exhibits a rim-brightened surface brightness, consistent with a shell-like emissivity distribution whose inner and outer boundaries are 4′ and 11′, respectively. These morphological differences between radio and X-rays suggest that the relativistic electrons are distributed homogeneously over the lobe volume, whereas the magnetic field is amplified toward the lobe rim region.

Original languageEnglish
JournalAstrophysical Journal
Volume546
Issue number1 PART 2
DOIs
Publication statusPublished - Jan 1 2001

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radio galaxies
particle energy
lobes
energy distribution
radio
emissivity
rims
energy
brightness
x rays
synchrotrons
power law
scattering
shell
magnetic field
microwaves
electron
radii
particle
distribution

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

X-ray measurements of the field and particle energy distributions in the west lobe of the radio galaxy NGC 1316 (Fornax A). / Tashiro, M.; Makishima, K.; Iyomoto, Naoko; Isobe, N.; Kaneda, H.

In: Astrophysical Journal, Vol. 546, No. 1 PART 2, 01.01.2001.

Research output: Contribution to journalArticle

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AU - Isobe, N.

AU - Kaneda, H.

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