Vla and Xmm - Newton Observations of Snr W 41 / Tev Γ - Ray Source Hess J 1834 - 087

The recently discovered extended TeV source HESS J1834-087 is associated with both a diffuse X-ray enhancement and a molecular cloud, projected at the center of an old radio supernova remnant G23.3-0.3 (SNR W41). New HI observations from the VLA Galactic Plane Survey (VGPS) show unambiguous structures associated with W41 in the radial velocity range of 53 to 63 km/s, so we obtain W41 distance of about 4±0.2 kpc. A new higher sensitivity VGPS continuum image of W41 at 1420 MHz shows faint emission in its eastern part not detected by previous observations, so we give a new angular size of 36 ′ ×30 ′ in b-l direction (average radius of 19 pc). We estimate for W41 a Sedov age of ∼8×10 4 yr. New XMM-Newton observation reveals diffuse X-ray emission within the HESS source and suggests an association between the X-ray and γ-ray emission. The high-resolution 13 CO images of W41 further reveal a giant molecular cloud (GMC) located at the center of W41, likely associated with W41 in the the radial velocity range of 61 to 66 km/s. These give first observational evidence that an old SNR encounters a GMC to emit TeV γ-rays in the GMC. Subject headings: supernova remnants:individual (W41)-γ-rays:individual (HESS J1834-087)