ner_tags: O O O O O O O O O O O O O O O O O B-Person I-Person I-Person I-Person I-Person O B-Person I-Person I-Person O O O O O O O O O O O O B-Organization I-Organization I-Organization I-Organization I-Organization I-Organization O O B-Grant B-Grant B-Grant B-Grant O B-Grant B-Grant O B-Organization I-Organization I-Organization I-Organization I-Organization I-Organization O O O O B-Grant B-Person O O O O B-Fellowship I-Fellowship B-Person O O O O B-Grant O O B-Organization B-Grant I-Grant I-Grant I-Grant I-Grant I-Grant I-Grant I-Grant
tokens: We are grateful to the anonymous referee for the constructive comments that helped us improve this paper. Prof. Neal J. Evans II and Dr. Kee-Tae Kim are also acknowledged for useful discussions. This work is supported by the National Natural Science Foundation of China through grants 11503035, 11573036, 11373009, 11433008 and 11403040, 11403041, the International ST Cooperation Program of China through the grant of 2010DFA02710. T.L. is supported by the EACOA fellowship. K.W. is supported by grant WA3628-1/1 through the DFG priority program 1573 “Physics of the Interstellar Medium.”