Poster Presentation Astronomical Society of Australia Annual Scientific Meeting including HWWS 2013

First results for MALT-45: A 7mm survey of the southern Galaxy (#235)

Christopher H Jordan 1 , Andrew Walsh , Maxim Voronkov , Simon Ellingsen 1 , Vicki Lowe
  1. University of Tasmania, Hobart, TAS, Australia

MALT-45 is an untargeted Galactic plane survey searching for tracers of high mass star formation (HMSF) at 7mm.  With the recent upgrades to the Australia Telescope Compact Array, we have been able to push the limits on observational efficiency to obtain a very sensitive blind survey in a short amount of time.  Specifically, MALT-45 uses a fast on-the-fly mapping with 6 seconds per pointing, which results in a quarter-square-degree region being mapped in approximately 14 hours. Each region is Nyquist sampled and collects data in 12 spectral lines.

The primary spectral lines of MALT-45 include: CS (1-0) - a high density gas tracer, which contrasts well with NH3 (1,1) from the similar HOPS survey; 44 GHz Class I methanol masers - the brightest of the Class I lines, it is poorly understood, and MALT-45 is one of the first surveys to thoroughly search for these masers; SiO (1-0) v=1,2,3 - typically associated with evolved stars, there have been rare associations with HMSF, and MALT-45 offers the potential to detect more.  Other lines include thermal SiO (1-0) v=0, thermal methanol, C34S, OCS, and radio recombination lines H51a and H53a.

Perhaps the most significant and innovative aspect of MALT-45 is the usage of ATCA autocorrelations.  Each antenna of the ATCA is similar to Mopra, and by using all 6 antennae simultaneously, have a 6 fold increase in sensitivity per unit observation time.  The autocorrelation data was only recently made available by the ATCA upgrade with the Compact Array Broadband Backend, and tools have been developed to allow this data processing.

We present the first 5 square-degrees (l = 330 - 335, b = -0.5 - +0.5) of the Galactic plane mapped by MALT-45.