MALT90: The Millimetre Astronomy Legacy Team 90 GHz Survey
  The Millimetre Astronomy Legacy Team 90 GHz (MALT90) survey aims to
characterise the physical and chemical evolution of high-mass star-forming
clumps. Exploiting the unique broad frequency range and on-the-fly mapping
capabilities of the Australia Telescope National Facility Mopra 22 m
single-dish telescope, MALT90 has obtained 3' x 3' maps toward ~2000 dense
molecular clumps identified in the ATLASGAL 870 um Galactic plane survey. The
clumps were selected to host the early stages of high-mass star formation and
to span the complete range in their evolutionary states (from prestellar, to
protostellar, and on to HII regions and photodissociation regions). Because
MALT90 mapped 16 lines simultaneously with excellent spatial (38") and spectral
(0.11 km/s) resolution, the data reveal a wealth of information about the
clump's morphologies, chemistry, and kinematics. In this paper we outline the
survey strategy, observing mode, data reduction procedure, and highlight some
early science results. All MALT90 raw and processed data products are available
to the community. With its unprecedented large sample of clumps, MALT90 is the
largest survey of its type ever conducted and an excellent resource for
identifying interesting candidates for high resolution studies with ALMA.
