The Environment around the Young Massive Star Cluster RSGC 1 and HESS
  J1837-069
  We report on Mopra observations toward the young massive star cluster RSGC 1,
adjoined by, and possibly associated with the gamma-ray source HESS J1837-069.
We measure the CO (J=1-0) distribution around the cluster and gamma-ray source,
and find that the cluster is slightly higher than the velocity ranges
associated with the Crux-Scutum arm. We reveal the cluster is associated with
much less molecular gas compared with other young massive clusters in the
Galaxy, Westerlund 1 (Wd 1) and 2 (Wd 2), which also radiate gamma-rays. We
find no other structures that would otherwise indicate the action of supernova
remnants, and due to the lack of material which may form gamma-rays by hadronic
interaction, we conclude that the gamma-rays detected from HESS J1837-069 are
not created through proton-proton interactions, and may more plausibly
originate from the pulsar that was recently found near RSGC 1.
