|The Millimetre Astronomy Legacy Team 90 GHz
(MALT90) Mopra survey has detected high-mass star-forming clumps with anomalous
N2H+/HCO+(1-0) integrated intensity ratios
that are either unusually high ("N2H+ rich") or unusually
low ("N2H+ poor"). With 3 mm observations from the ATCA,
two N2H+ rich clumps and two N2H+
poor clumps were imaged. In these clumps, the N2H+ rich
anomalies arise from extreme self-absorption of the HCO+ line.
G333.234-00.061 (above) contains two of the most massive protostellar cores
known with diameters of less than 0.1 pc, separated by a projected distance
of only 0.12 pc. The white contours and the blue color scale show the 3 mm
continuum, blue contours show the 8 micron Spitzer IRAC emission, and the
X symbols mark locations of many different types of masers. These extreme
self-absorbed high-mass star-forming clumps observed with Mopra may indicate
the locations of the most massive star-forming sites.