Interstellar molecular clouds are sources of gamma rays through the interactions with cosmic ray protons followed by production of neutral pions which decay into gamma rays .
We present new observations of the TeV gamma ray SNR RXJ 1713.7-3946 and the W28 region with the NANTEN2 sub-mm telescope in the ^ { 12 } CO J = 2–1 , 4–3 and 7–6 emission lines .
In RXJ 1713.7-3946 we confirm that the local molecular gas having velocities around -10 km s ^ { -1 } ( with respect to the local standard of rest ) shows remarkably good spatial correlations with the SNR .
We show that the X ray peaks are well correlated with the molecular gas over the whole SNR and suggest that the interactions between the SNR and the molecular gas play an important role in cosmic ray acceleration via several ways including magnetic field compression .
The J = 4–3 distribution shows a compact and dense cloud core having a size of \sim 1 pc as well as a broad wing towards peak C of the CO distribution .
The cloud core shows a remarkable anti-correlation with the Suzaku X ray image and is also associated with hard gamma rays as observed with HESS .
Based on these findings we present a picture that peak C is a molecular clump survived against the impact of the SN blast waves and is surrounded by high energy electrons emitting the X ray .
The TeV gamma ray distribution is , on the other hand , more extended into the molecular gas , supporting the hadronic origin of gamma ray production .
W 28 is one of the most outstanding star forming regions exhibiting TeV gamma rays as identified through a comparison between the NANTEN CO dataset and HESS gamma ray sources in the Galactic plane .
In the W 28 region , we show the CO J = 2–1 distribution over the whole region as well as the detailed image of the two TeV gamma ray peaks .
One of the two peaks show strong CO J = 7–6 emission , suggesting high excitation conditions in this high mass star forming core .
A pursuit for the detailed mechanism to produce gamma rays is in progress .
Finally , we discuss results of numerical simulation of the time dependent gamma ray image towards an ensemble of molecular clouds in the Galactic plane .