ORIGIN OF THE X-RAYS AND POSSIBLE GeV-TeV EMISSION FROM THE WESTERN HOT SPOT OF PICTOR A

Journal Article · Mon Aug 10 04:00:00 EDT 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/701/1/423; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21313672

Jin, Zhang; Bai, J -M; Liang, Chen; Xian, Yang ^[1]

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1. National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, P.O. Box 110, Kunming, Yunnan 650011 (China)

Pictor A is a nearby Fanaroff-Riley class II (FR II) radio galaxy with a bright hot spot, the western hot spot. Observation of high polarization in the optical emission of the hot spot indicates that the optical emission could be synchrotron radiation of relativistic electrons in the hot spot. These electrons may be able to produce high-energy {gamma}-ray photons through inverse Compton scattering. We use single-zone and multizone synchrotron + synchrotron self-Compton models to fit the observed spectral energy distribution (SED) from the radio to the X-ray band of the hot spot. Our results show that in the case of a much weaker magnetic field strength than the equipartition magnetic field, both the single-zone and multizone models can fit the SED, but the multizone model significantly improves the fit. The two models predict the hot spot as a GeV-TeV source, which might be marginally detectable with Fermi/LAT and H.E.S.S. The inverse Compton scattering of cosmic microwave background is also considered, but its contribution to GeV-TeV emission is negligible. Note that under the equipartition condition, the SED can also be fitted with the multizone model, but the predicted flux at >10{sup 22} Hz is too weak to be detectable. The detection of TeV {gamma}-rays from this FR II radio galaxy, if confirmed, would establish a new subclass of extragalactic sources in this energy regime since most of the active galactic nuclei detected to date at TeV energies are high-energy-peaked BL Lac objects.

• OSTI ID: 21313672
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 701; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

99 GENERAL AND MISCELLANEOUS
COMPTON EFFECT
COSMIC ELECTRONS
COSMIC PHOTONS
ENERGY SPECTRA
GALAXY NUCLEI
GAMMA RADIATION
GEV RANGE
HOT SPOTS
MAGNETIC FIELDS
RADIO GALAXIES
RELATIVISTIC RANGE
RELICT RADIATION
TEV RANGE
X-RAY GALAXIES