The APEX Submillimetre Dust Continuum Survey of the Inner Galaxy (ATLASGAL)

The still poorly understood early stages of massive star formation (MSF) are presently a pressing topic in astronomy. Since they evolve quickly, are rare and at larger distances than their lower mass siblings, only Galaxy-wide surveys can find significant samples of massive stars in their early stages. Such samples are needed since the evolutionary sequence in high-mass star formation and the associated timescales are not understood yet. In the past, samples biased towards evolved stages of the formation process, e.g. based on IR colour criteria compact cm continuum or maser emission were successfully studied and yielded important insights into these later stages. Complementary, colder objects were revealed in mid-infrared surveys as so-called infrared dark clouds. Since high density clumps consist of gas which is about to form star clusters, there is a strong need for large scale surveys in a (cold) dense gas tracer such as the submm dust continuum. This led us to conduct the first unbiased survey of the inner Galactic Plane at 870 ~m (ATLASGAL, Schuller et al. 2009) to study (i) massive star formation throughout the Galaxy, (ii) the pre stellar/precluster initial mass function down to a few solar masses, (iii) to probe the large scale structure of the cold ISM and (iv) to associate the cold dust with Galactic surveys that have been conducted at other wavelengths with the VLA and Spitzer. At 870um and from a site in the southern hemisphere, it is complementary to the lower angular resolution 1.1mm Bolocam Galactic Plane Survey in the north and the ongoing Herschel Hi-GAL survey. Based on ATLASGAL, already almost 30 papers have been published, some with immediate strong impact (e.g. the Deharveng et al. 2010 study of dense clumps associated with infrared bubbles). A considerable fraction of the data is now publicly available to the community and a first compact source catalogue has recently been published (Contreras et al. 2013).