Spitzer Space Telescope - General Observer Proposal #50575


Dust in the Wind: Mapping the Nearest Galactic Superwind with the IRS on Spitzer

Principal Investigator: Lee Armus
           Institution: Spitzer Science Center

     Technical Contact: Lee Armus, Spitzer Science Center

Co-Investigators: 
Francois Boulanger, IAS                                               
Bruce Draine, Princeton University                                    
Chad Engelbracht, University of Arizona                               
Pierre Guillard, IAS                                                  
Timothy Heckman, Johns Hopkins University                             
David Hollenbach, NASA-Ames Research Center                           
Charles Hoopes, Naval Research Lab                                    
Matthew Lehnert, Observatoire de Paris                                
Kartik Sheth, Spitzer Science Center                                  
Patrick Shopbell, California Institute of Technology                  
John David Smith, University of Arizona                               
Jason Surace, Spitzer Science Center                                  
Fabian Walter, MPIA                                                   

Science Category: starburst galaxies 
 Observing Modes: IrsMap 
  Hours Approved: 35.7 

Abstract:
Galactic-scale superwinds, driven by the collective effect of massive stars and
supernovae, have been invoked as a source of heating and metallicty enrichment
of both the intra-cluster and inter-galactic medium. There is abundant
morphological, physical, and kinematic evidence for superwinds in nearby
starburst and infrared-luminous galaxies. At high redshifts, superwinds are
found in Lyman-break galaxies at z=2-3. M82 is the nearest, brightest and
best-studied starburst galaxy with multi-wavelength (UV, X-ray, Halpha, CO,
etc.) evidence for a superwind. Spitzer IRAC imaging of M82 has revealed a
spectacular, large-scale nebula along the outflow axis that is strongly emitting
in the 7.7+8.6 micron PAH bands. Spitzer IRS maps of the base of the wind reveal
a complex structure of dust, ionized gas, and molecular gas, emitting strongly
in PAH features and H2 lines. However, most of the wind and the dust halo in M82
remains unobserved with the IRS. Here, we propose to obtain IRS maps of the dust
in the wind at larger radii, outside the X-ray/UV ionization cone, and in the
outer parts of the wind. The IRS maps proposed here will triple the wind area
mapped with the IRS above the plane, and reach out more than a factor of two in
radius. M82 provides a unique opportunity to study a superwind in unprecedented
detail. When combined with the existing maps, the data proposed here will
provide us with the most complete physical picture of the interaction of a dusty
wind with a galaxy halo that can be achieved with Spitzer.