The integrated 13CO emission from the ~1 degree square region of the molecular cloud complex observed by Mopra in the Delta Quadrant Survey. The Mopra beam size at the frequency of the J=1-0 13CO transition is 30 arcsec.

A comprehensive model that explains how stars form remains elusive to astronomers. It is generally accepted that the gas and dust in giant molecular clouds collapses to form a gravitationally-bound nascent stellar system, but what causes and regulates this collapse? The formation of the minority of objects that are single, low-mass systems is well-studied, but the obscuration provided by the dense dust in sites of massive star formation, coupled with their relatively large distances from us, make these objects more difficult to observe and hence to study. In recent years, a potentially comprehensive model of star formation has arisen that focuses on the role played by turbulence in driving and regulating stellar birth. The precise origin of the turbulence is unknown but may arise due to large-scale Galactic flows of gas or expanding supernova bubbles. The models detail how the turbulence cascades across all spatial scales and can both encourage the formation of clumps in molecular clouds and disrupt any already-forming clumps, hence it can both drive and regulate the rate of star birth.

In order to provide observational constraints for this promising theory, we have developed a programme of molecular spectral line observations with the Mopra telescope of a degree-sized region of a giant molecular cloud complex situated in the fourth quadrant (hence ‘Delta Quadrant’) of our Galaxy. The express purpose of this programme is to detect the effects of turbulence in the molecular cloud and compare it to the local star forming efficiency in order to elucidate the link between the two. The programme began in 2004 with 10 weeks spent mapping the molecular cloud in the ¹³CO (J=1-0) 110-GHz transition. The image shows the total intensity map of the carbon monoxide molecule’s emission.

The observers who dedicated their time to make these observations were primarily members of the UNSW star formation group – Indra Bains, Michael Burton, Maria Cunningham, Steve Longmore, Cormac Purcell, Patricia Sparks, Andrew Walsh and Tony Wong – plus some dedicated ‘friends’ of the group such as Bruce Fulton and Gary Deragopian. Typically, two observers spent a week at a time at the telescope, 7 hours drive from Sydney in the Warrumbungles National Park, near the town of Coonabarabran.

We are currently analysing the ¹³CO data and using specific analysis techniques to investigate the signatures of turbulence present in this molecular cloud complex.

Indra Bains