Protostars and Planets VI, Heidelberg, July 15-20, 2013
Chemical diversity in W33
Immer, Katharina (Max-Planck-Institut fuer Radioastronomie)
Galvan-Madrid, Roberto (ESO)
Menten, Karl (Max-Planck-Institut fuer Radioastronomie)
The W33 complex is an ideal object to study massive star formation since it contains molecular
clouds in different evolutionary stages within a small area on the sky. Recent trigonometric parallax
observations of water masers in the complex give an accurate distance to W33 and show that W33
is one connected star forming complex. Thus, W33 allows the study of star formation processes
under similar conditions along an evolutionary sequence, from quiescent infrared dark clouds over
\"intermediate\" hot cores to ultra-compact HII (UCHII) regions.
I will present spectral line observations of six W33 clouds along this evolutionary sequence, taken with the Submillimeter Array at 230 GHz and the Atacama Pathfinder Experiment telescope at 280 GHz. The spectra show significant differences in the chemistry of the clouds, supporting the identification of different evolutionary stages in the complex. While in the quiescent clouds the line emission comes mostly from CO and H2CO, the spectra of the clouds in the \"intermediate\" hot core phase are much line-richer. Surprisingly, in the most evolved cloud (UCHII region phase) much less molecules than in the clouds in the hot core phase are detected. Thus, molecules that are not detected in the UCHII region phase compared to the hot core phase may be used as chemical clocks for this intermediate phase.
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