A multi-wavelength study of the unidentified TeV gamma-ray source HESS J1626-490

Abstract

HESS J1626-490, so far only detected with the H.E.S.S. array of imaging atmospheric Cherenkov telescopes, could not be unambiguously identified with any source seen at lower energies. Therefore, we analyzed data from an archival XMM-Newton observation, pointed towards HESS J1626-490, to classify detected X-ray point-sources according to their spectral properties and their near-infrared counterparts from the 2MASS catalog. Furthermore, we characterized in detail the diffuse X-ray emission from a region compatible with the extended VHE signal. To characterize the Interstellar Medium surrounding HESS J1626-490 we analyzed ${}^{12}$CO(J=1-0) molecular line data from the NANTEN Galactic plane survey, HI data from the Southern Galactic Plane Survey and Spitzer data from the GLIMPSE and MIPSGAL surveys. None of the detected X-ray point sources fulfills the energetic requirements to be considered as the synchrotron radiation (SR) counterpart to the VHE source assuming an Inverse Compton (IC) emission scenario. We did not detect any diffuse X-ray excess emission originating from the region around HESS J1626-490 above the Galactic Background and the derived upper limit for the total X-ray flux disfavors a purely leptonic emission scenario for HESS J1626-490. We found a good morphological match between molecular and atomic gas in the -27km/s to -18km/s line-of-sight velocity range and HESS J1626-490. The cloud has a mass of 1.8$times10^4$M${}_{odot}$ and is located at a mean kinematic distance of $d$ = 1.8 kpc. Furthermore, we found a density depression in the HI gas at a similar distance which is spatially consistent with the SNR G335.2+00.1. We discuss various scenarios for the VHE emission, including the CO molecular cloud being a passive target for cosmic ray protons accelerated by the nearby SNR G335.2+00.1.

9 pages, 10 figures, A&A in press, updated to the final version

References in corpus (7)

• Fermi Large Area Telescope First Source Catalog
• HESS VHE Gamma-Ray Sources Without Identified Counterparts
• Observation of Extended VHE Emission from the Supernova Remnant IC 443 with VERITAS
• The XMM-Newton EPIC Background and the production of Background Blank Sky Event Files
• Exploring a SNR/Molecular Cloud Association Within HESS J1745-303
• Spatially resolved XMM-Newton analysis and a model of the nonthermal emission of MSH 15-52
• Gamma ray signatures of ultra high energy cosmic ray accelerators: electromagnetic cascade versus synchrotron radiation of secondary electrons

Cited by in corpus (7)

• The H.E.S.S. Galactic plane survey
• The 1st Fermi Lat Supernova Remnant Catalog
• Distances, Radial Distribution and Total Number of Galactic Supernova Remnants
• Dense molecular gas at 12 mm towards Galactic TeV gamma-ray sources
• HESS J1818-154, a new composite supernova remnant discovered in TeV gamma rays and X-rays
• The Age Evolution of the Radio Morphology of Supernova Remnants
• Chandra observations of the HII complex G5.89-0.39 and TeV gamma-ray source HESSJ1800-240B