Spitzer Space Telescope - Guaranteed Time Observer Proposal #40051


Spectral Mapping of W49A

Principal Investigator: Bernhard Brandl
           Institution: University of Leiden

     Technical Contact: Bernhard Brandl, University of Leiden

Co-Investigators: 
Edward Churchwell, University of Wisconsin-Madison                    
Dan Watson, University of Rochester                                   
Jim Houck, Cornell University                                         

Science Category: HII regions 
 Observing Modes: IrsMap 
  Hours Approved: 3.6 

Abstract:
We propose to spectrally map the massive Galactic HII region W49A with
Spitzer-IRS in low-resolution mode. W49A is one of the most luminous and
prolific massive star formation regions in the disk of the Milky Way. W49A is
unique among massive Galactic star forming regions in that it contains about 40
separate ultra-compact HII regions and several massive, evolved OB clusters,
embedded in 10E6 solar masses of molecular gas -- all located within a region of
about 55pc. Our previous IRAC observations have shown that these components are
closely related. Here we propose to complete our 5-15um spectral map of the
central part of W49A to study the dynamics, physics and chemistry in the core of
a luminous starburst region at reasonably high spatial resolution. The results
will be of great importance to study the formation of massive stars and their
interplay with the surrounding ISM. Previous GTO observations have demonstrated
the technical feasibility of this project but unfortunately missed (due to
scheduling reasons) the most relevant part of the region.