VLA and XMM-Newton Observations of the SNR W41/TeV Gamma-Ray Source HESS J1834-087

The recently discovered extended TeV source HESS J1834-087 is associated withboth a diffuse X-ray enhancement and a molecular cloud, projected at the centerof an old radio supernova remnant G23.3-0.3 (SNR W41). New HI observations fromthe VLA Galactic Plane Survey (VGPS) show unambiguous structures associatedwith W41 in the radial velocity range of 53 to 63 km/s, so we obtain for W41 adistance of 4+-0.2 kpc. A new higher sensitivity VGPS continuum image of W41 at1420 MHz shows faint emission in its eastern part not detected by previousobservations, so we give a new angular size of 36'x30' in b-l direction(average radius of 19 pc). We estimate for W41 a Sedov age of ~10e5 yr. NewXMM-Newton observation reveals diffuse X-ray emission within the HESS sourceand suggests an association between the X-ray and Gamma-ray emission. Thehigh-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 theradial velocity range of 61 to 66 km/s. Altogether, the new observations can beinterpreted as providing the first evidence that an old SNR encounters a GMC toemit TeV gamma-rays in the cloud material.Comment: 11 page, 5 figs, 1 table, accepted by ApJ letter