A Self-Consistent Model for the Broad-band Spectrum of Sgr A East at the Galactic Center

Abstract

Sgr A East is a very prominent elongated shell structure surrounding (though off-centered from) the Galactic nucleus. Its energetics (~4x10^52 ergs), based on the power required to carve out the radio synchrotron remnant within the surrounding dense molecular cloud, appear to be extreme compared to the total energy (~10^51 ergs) released in a typical supernova (SN) explosion. Yet it shares several characteristics in common with SN remnants (SNRs), the most significant of which is the ~0.1-10 GeV gamma-ray spectrum measured by EGRET, if we associate the Galactic center source 2EGJ1746-2852 with this nonthermal shell. We here show that the highest-energy component in Sgr A East's spectrum, like that of SNRs, can be fitted with the gamma-rays produced in neutral pion decays. Further, we demonstrate in a self-consistent manner that the leptons released in the associated charged pion decays produce an e+e- distribution that can mimic a power-law with index ~3, like that inferred from the VLA data for this source. These relativistic electrons and positrons also radiate by bremsstrahlung, and inverse Compton scattering with the intense IR and UV fields from the nucleus. We show that the overall emissivity calculated in this way may account for Sgr A East's broadband spectrum ranging from GHz frequencies all the way to TeV energies, where Whipple has thus far set an upper limit to the flux corresponding to a 2.5-sigma signal above the noise.

14 pages, including 3 eps figures, LaTeX using aasms4.sty, accepted for publication in Astrophysical Journal Letters Replacement includes additional reference

References in corpus (3)

• Gamma-ray production in supernova remnants
• Gamma-ray Emission From Advection-Dominated Accretion Flows Around Black Holes: Application to the Galactic Center
• On the Nature of the EGRET Source at the Galactic Center

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• ALMA Observations of the Terahertz Spectrum of Sagittarius A*
• A Kinship between the EGRET SNR's and Sgr A East
• Discovering Long Wavelength Neutrino Oscillations in the Distorted Neutrino Spectrum of Galactic Supernova Remnants
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• Diffuse TeV Emission at the Galactic Centre
• Neutrinos from the Galactic Center in the Light of its Gamma-Ray Detection at TeV Energy
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