ATLASGAL --- Molecular fingerprints of a sample of massive star forming
  clumps
  We have conducted a 3-mm molecular-line survey towards 570 high-mass
star-forming clumps, using the Mopra telescope. The sample is selected from the
10,000 clumps identified by the ATLASGAL survey and includes all of the most
important embedded evolutionary stages associated with massive star formation,
classified into five distinct categories (quiescent, protostellar, young
stellar objects, \hii\ regions and photo-dominated regions). The observations
were performed in broadband mode with frequency coverage of 85.2 to 93.4\,GHz
and a velocity resolution of $\sim$0.9\,\kms, detecting emission from 26
different transitions. We find significant evolutionary trends in the detection
rates, integrated line intensities, and abundances of many of the transitions
and also identify a couple of molecules that appear to be invariant to changes
in the dust temperature and evolutionary stage (N$_2$H$^+$\,(1-0) and
HN$^{13}$C\,(1-0)). We use the K-ladders for CH$_3$C$_2$H\,(5-4) and
CH$_3$CH\,(5-4) to calculate the rotation temperatures and find $\sim$1/3 of
the quiescent clumps have rotation temperatures that suggest the presence of an
internal heating source. These sources may constitute a population of very
young protostellar objects that are still dark at 70\,\mum\ and suggest that
the fraction of truly quiescent clumps may only be a few per cent. We also
identify a number of line ratios that show a strong correlation with the
evolutionary stage of the embedded objects and discuss their utility as
diagnostic probes of evolution.
