On the possible correlation of Galactic very-high energy source locations and enhancements of the surface density in the Galactic plane

Abstract

Aims. The association of very-high energy sources with regions of the sky rich in dust and gas has been noticed in the study of individual very-high energy (VHE; E > ∼ 100 GeV) sources. However, the statistical significance of this correlation for the whole population of TeV detections has not been assessed yet. Here, we present a study of the association of VHE sources in the central Galactic region with positions of enhanced material content. Methods. We obtain estimates of the material content through two classical tracers: dust emission and intensity of the 12 CO(1 → 0) line. We make use of the recently released all-sky maps of astrophysical foregrounds of the Planck Collaboration, and of an extensive existing CO mapping of the Galactic sky. To test the correlation, we construct randomized samples of VHE source positions starting from the inner Galactic plane survey sources detected by the High Energy Stereoscopic System (H.E.S.S.) array. Results. We find hints of a positive correlation between positions of VHE sources and regions rich in molecular material, which reaches the 3.9σ level in the best of cases. The latter confidence is however decreased if variations in the selection criteria are considered, which lead us to conclude that a positive correlation cannot be firmly established yet. Forthcoming VHE facilities will be needed to firmly establish the correlation.

Galactic very high energy sources and enhancements of material content

“…The work presented here is part of works published previously in Pedaletti et al ( 2014) and Pedaletti et al ( 2015).…”

Dense molecular gas at 12 mm towards Galactic TeV gamma-ray sources

“…Collaboration et al 2015a). (Pedaletti et al 2014) show that regions of high stellar activity within the central Galactic region, traced by dust emission and CO, could be correlated with TeV emission.…”