Spitzer Space Telescope - Legacy General Observer Proposal #30570


GLIMPSE 3D:  The Vertical Stellar and Interstellar Structure of the
Inner Galaxy

Principal Investigator: Robert Benjamin
           Institution: University of Wisconsin-Whitewater

Co-Investigators: 
Ed Churchwell, University of Wisconsin-Madison                        
Marilyn Meade, University of Wisconsin-Madison                        
Brian Babler, University of Wisconsin-Madison                         
Barbara Whitney, Space Science Institute                              
Michael Merrifield, University of Nottingham                          
Martin Cohen, University of California-Berkeley                       
Christer Watson, Manchester College                                   
Joris Blommaert, Instituut voor Sterrenkunde, K.U. Leuven             

Science Category: star formation 
 Observing Modes: IracMap 
  Hours Approved: 254.5 

Abstract:
Galaxies are three-dimensional stellar systems, but for external
galaxies, we are limited to studying a two dimensional projection.
There is only one system where we can obtain a three dimensional view:
our own Milky Way.  Fundamental questions of vertical Galactic stellar
structure can be most profitably pursued in investigations of our own
Galaxy, but studies of stellar distributions with 2MASS and other near
IR surveys in the inner Galaxy have been fundamentally limited by
extinction.  Investigations with COBE/DIRBE have shown that the
mid-infrared is the optimum wavelength range for studies of Galactic
stellar structure;  early results using data from the GLIMPSE confirm
this.  However, GLIMPSE data is insufficient to constrain the vertical
scaleheights of the different components of the Galaxy.  We propose to
use IRAC for 254.5 hours to map 112 square degrees in a series of
latitude strips above and below the Galactic plane in all four IRAC
bands.  These latitude strips will stretch up to abs(b)<4.2 deg around
the central region of the Galaxy (abs(l)<2 deg) and include Baade's
window.  They will cover abs(b)<3 deg for six latitude strips centered
at l=3.5, 11, 15, 18.5, 25,and 30  deg.  The resulting dataset can be
used to determine the scaleheight of the Galactic bulge, the Galactic
bar(s), the thin stellar disk, the Galactic ring, and the inner spiral
arms, with a variety of different stellar tracers.  Mosaicked images
will be supplied to community, and a point source Catalog and Archive
will be produced and merged with the 2MASS catalog, allowing the study
of SEDs from 1-8 microns for all sources.  This project will also
enable many other scientific investigations, including off-plane star
formation, studies of diffuse IR cirrus, and the vertical scaleheights
of different stellar populations.  The understanding of Milky Way
stellar structure gained from this project will be an important legacy
for Galactic and extragalactic researchers alike.