HESS J1912+101 is a shell-like TeV source that has no clear counterpart in multi-wavelength. Using the Purple Mountain Observatory Delingha 13.7 m millimeter-wavelength telescope, we reveal that V(LSR)~ 60 km/s molecular clouds (MCs) are concentrated toward the extended high-energy source. In combination with the VGPS HI and COHRS CO(3-2) data, we found that the shocked molecular gas and high-velocity neutral atomic shells is also associated with the 60 km/s MCs. The prominent wing profiles up to 80km/s seen in CO, as well as the high-velocity HI shells up to 100 km/s, exhibit striking redshifted-broadening relative to the quiescent gas at a systematic velocity of 60 km/s. We argue that the large-scale perturbation in this region may originate from an old supernova remnant (SNR). The distance, age, and radius of the SNR are 4.1 kpc, (0.7--2.0) x10^5 years, and 29.0 pc. The 60 km/s MCs and the disturbed gas are indeed found to coincide with the bright TeV source, supporting the physical association between them. Naturally, the shell-like TeV emission comes from the decay of neutral pions produced by interactions between the accelerated hadrons from the SNR and the surrounding high-density molecular gas.

By with SU Yang

Figure 1.12CO (J=1–0, blue),13CO (J=1–0, green), and C18O (J=1–0, red) intensity map toward HESS J1912+101 in the 58.5–62.0 kms−1 interval. The two yellow circles indicate the outer and inner TeV shells of HESS J1912+101 (Aharonian et al.2008a; Gottschall et al.2016), while the red and the white circles indicate the two pulsars(Morris et al.2002; Hobbs et al.2004)and the shocked clouds. The white box indicates the region shown in Figure2.

Our study has greatly benefitted from the Milky Way Imaging Scroll Painting Project (MWISP), which is a large, unbiased, and high-quality CO and its isotopes survey from Galactic longitude of -10 to 250 degrees and Galactic latitudes from -5 to 5 degrees. The CO data with high spatial (~50'') and velocity (~0.2 km/s) resolution provide us with a good opportunity in studying the molecular environment of extended sources from large scale to small scale. The paper was published in the Astrophysical Journal (2017, ApJ, 845, 48). Detailed information of the paper can be found at: http://adsabs.harvard.edu/abs/2017ApJ...845...48S