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

doi:10.1051/0004-6361/201220270

arXiv · 1211.6782

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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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 gamma-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 gamma-ray source in the LAT dataset, in which it appears as a steady gamma-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 gamma-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 gamma-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 gamma-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.

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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. 2012-11-28. Fermi-LAT and Suzaku Observations of the Radio Galaxy Centaurus B. https://doi.org/10.1051/0004-6361/201220270

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