The morphology of hadronic emission models for the gamma-ray source at the galactic center

Abstract

Recently, detections of a high-energy γ-ray source at the position of the Galactic center have been reported by multiple γ-ray telescopes, spanning the energy range between 100 MeV and 100 TeV. Analysis of these signals strongly suggests the TeV emission to have a morphology consistent with a point source up to the angular resolution of the HESS telescope (approximately 3pc), while the point-source nature of the GeV emission is currently unsettled, with indications that it may be spatially extended. In the case that the emission is hadronic and in a steady state, we show that the expected γ-ray morphology is dominated by the distribution of target gas, rather than by details of cosmic-ray injection and propagation. Specifically, we expect a significant portion of hadronic emission to coincide with the position of the circumnuclear ring, which resides between 1 and 3pc from the Galactic center. We note that the upcoming Cherenkov Telescope Array (CTA) will be able to observe conclusive correlations between the morphology of the TeV γ-ray source and the observed gas density, convincingly confirming or ruling out a hadronic origin for the γ-ray emission. © 2012. The American Astronomical Society. All rights reserved.