Fermi -LAT and Suzaku observations of the radio galaxy Centaurus B

J. Katsuta, Y. T. Tanaka, L. Stawarz, S. P. O'Sullivan, C. C. Cheung, J. Kataoka, S. Funk, T. Yuasa, H. Odaka, T. Takahashi, J. Svoboda

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15 Citations (Scopus)

Abstract

Centaurus B is a nearby radio galaxy positioned in the southern hemisphere close to the Galactic plane. Here we present a detailed analysis of about 43 months of accumulated Fermi-LAT data of the γ-ray counterpart of the source initially reported in the 2nd Fermi-LAT catalog, and of newly acquired Suzaku X-ray data. We confirm its detection at GeV photon energies and analyze the extension and variability of the γ-ray source in the LAT dataset, in which it appears as a steady γ-ray emitter. The X-ray core of Centaurus B is detected as a bright source of a continuum radiation. We do not detect, however, any diffuse X-ray emission from the known radio lobes, with the provided upper limit only marginally consistent with the previously claimed ASCA flux. Two scenarios that connect the X-ray and γ-ray properties are considered. In the first one, we assume that the diffuse non-thermal X-ray emission component is not significantly below the derived Suzaku upper limit. In this case, modeling the inverse-Compton emission shows that the observed γ-ray flux of the source may in principle be produced within the lobes. This association would imply that efficient in-situ acceleration of the radiating electrons is occurring and that the lobes are dominated by the pressure from the relativistic particles. In the second scenario, with the diffuse X-ray emission well below the Suzaku upper limits, the lobes in the system are instead dominated by the magnetic pressure. In this case, the observed γ-ray flux is not likely to be produced within the lobes, but instead within the nuclear parts of the jet. By means of synchrotron self-Compton modeling, we show that this possibility could be consistent with the broad-band data collected for the unresolved core of Centaurus B, including the newly derived Suzaku spectrum.

Original languageEnglish
Article numberA66
JournalAstronomy and Astrophysics
Volume550
DOIs
Publication statusPublished - 2013 Feb 4

Keywords

  • Acceleration of particles
  • Galaxies: individual: Centaurus B
  • Galaxies: jets
  • Gamma rays: galaxies
  • Radiation mechanisms: non-thermal
  • X-rays: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Katsuta, J., Tanaka, Y. T., Stawarz, L., O'Sullivan, S. P., Cheung, C. C., Kataoka, J., Funk, S., Yuasa, T., Odaka, H., Takahashi, T., & Svoboda, J. (2013). Fermi -LAT and Suzaku observations of the radio galaxy Centaurus B. Astronomy and Astrophysics, 550, [A66]. https://doi.org/10.1051/0004-6361/201220270