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The Australia Telescope National Facility Colloquium
15:00-16:00 Mon 04 Nov 2013

James Jackson

(Boston University)

James Jackson Colloquium -- The Millimeter Astronomy Legacy Team 90 GHz Survey (MALT 90)

I present results from the recently completed MALT 90 Survey, a multi-line survey of molecular emission from dense, high-mass star-forming clumps. MALT90 uses the Mopra 22-m telescope to map 16 molecular lines simultaneously toward a sample of 2,000 dense molecular clumps identified by the 870 micron ATLASGAL continuum survey. I will describe three results: (1) a technique to find distances and Galactic structure. The star forming cores delineate spiral arms, and we have discovered the heretofore missing segment of the Scutum-Centaurus arm on the far side of the Galaxy; (2) compelling evidence for changing physical and chemical conditions of star-forming clumps as they evolve from cold "pre-stellar" phase, to accreting "protostellar phases", and on to full-fledged high-mass main sequence stars. A preliminary evolutionary scheme based on mid-infrared properties is confirmed. The temperature increases monotonically, and we see significant changes in chemistry, in particular the HCN/HNC and N2H+/HCO+ abundance ratios; and (3) the extension of the Gao and Solomon relation between molecular line and infrared luminosity, first established for entire galaxies, to the scale of individual cores.


Contact

Alex Hill
alex.hill@csiro.au

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