New unidentified Galactic H.E.S.S. sources

TL;DR

This paper reports on newly discovered unidentified very high energy gamma-ray sources in the Galactic Plane by H.E.S.S., highlighting the challenges in identifying their origins due to lack of counterparts at other wavelengths.

Contribution

It presents new unidentified VHE gamma-ray sources discovered by H.E.S.S. during the 2005-2008 Galactic Plane Survey, emphasizing their ambiguous nature and the difficulty in determining their origins.

Findings

Several new VHE gamma-ray sources identified.

Many sources lack counterparts at other wavelengths.

Some sources have multiple possible origin scenarios.

Abstract

H.E.S.S. is one of the most sensitive instruments in the very high energy (VHE; > 100 GeV) gamma-ray domain and has revealed many new sources along the Galactic Plane. After the successful first VHE Galactic Plane Survey of 2004, H.E.S.S. has continued and extended that survey in 2005-2008, discovering a number of new sources, many of which are unidentified. Some of the unidentified H.E.S.S. sources have several positional counterparts and hence several different possible scenarios for the origin of the VHE gamma-ray emission; their identification remains unclear. Others have so far no counterparts at any other wavelength. Particularly, the lack of an X-ray counterpart puts serious constraints on emission models. Several newly discovered and still unidentified VHE sources are reported here.