A multi-transition molecular line study of infrared dark cloud
  G331.71+00.59
  Using archive data from the Millimeter Astronomy Legacy Team Survey at 90 GHz
(MALT90), carried out using the Mopra 22-m telescope, we made the first
multi-transition molecular line study of infrared dark cloud (IRDC) MSXDC
G331.71+00.59. Two molecular cores were found embedded in this IRDC. Each of
these cores is associated with a known extended green object (EGO), indicating
places of massive star formation. The HCO+ (1-0) and HNC (1-0) transitions show
prominent blue or red asymmetric structures, suggesting outflow and inflow
activities of young stellar objects (YSOs). Other detected molecular lines
include H13CO+ (1-0), C2H (1-0), HC3N (10-9), HNCO(404-303) and SiO (2-1),
which are typical of hot cores and outflows. We regard the two EGOs as evolving
from the IRDC to hot cores. Using public GLIMPS data, we investigate the
spectral energy distribution of EGO G331.71+0.60. Our results support this EGO
being a massive YSO driving the outflow. G331.71+0.58 may be at an earlier
evolutionary stage.
