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D.A. Dale (Wyoming), G.J. Bendo, C.W. Engelbracht, K.D. Gordon (Arizona), M.W. Regan (STScI), L. Armus (Caltech), J.M. Cannon (MPIA), D. Calzetti (STScI), B.T. Draine (Princeton), G. Helou (Caltech), R.D. Joseph (Hawaii), R.C. Kennicutt (Arizona), A. Li (Missouri), E.J. Murphy (Yale), H. Roussel (Caltech), F. Walter (MPIA), H.M. Hanson (Wyoming), D.J. Hollenbach (NASA Ames), T.H. Jarrett (Caltech), L.J. Kewley (Hawaii), C.A. Lamanna (Wyoming), C. Leitherer, M. Meyer (STScI), G.H. Rieke, M.J. Rieke (Arizona), K. Sheth (Caltech), J.D.T. Smith (Arizona), M.D. Thornley (Bucknell)
The Spitzer Infrared Nearby Galaxies Survey (SINGS) is carrying out a comprehensive multi-wavelength survey on a sample of 75 nearby galaxies. The 1-850~\micron\ spectral energy distributions are presented for the first portion of the SINGS sample using broadband imaging data from Spitzer, 2MASS, ISO, IRAS, and SCUBA. The infrared colors derived from the globally-integrated Spitzer data are generally consistent with the previous generation of models that were developed based on global data for normal star-forming galaxies, though significant deviations are observed. Spitzer's excellent sensitivity and resolution also allow a detailed investigation of the infrared spectral energy distributions for various locations within the three large, nearby galaxies NGC~3031 (M~81), NGC~5194 (M~51), and NGC~7331. A wide variety of spectral shapes are found within each galaxy, especially for NGC~3031, the closest of the three targets and thus the galaxy for which the smallest spatial scales can be explored. The local star formation rate, as gauged by H\alpha emission, is shown to strongly correlate with local infrared fluxes and colors. If the galaxy-to-galaxy variations in spectral energy distributions seen in our sample are representative of the range present at high redshift then extrapolations of total infrared luminosities and star formation rates from the observed 24~\micron\ flux will be uncertain at the factor-of-five level. The corresponding uncertainties in the redshifted 8.0~\micron\ flux (e.g. observed 24~\micron\ flux for a z = 2 source) are factors of 5--10. Considerable caution should be used when interpreting such extrapolated infrared luminosities.
Support for this work, part of the Spitzer Space Telescope Legacy Science Program, was provided by NASA through Contract Number 1224769 issued by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407.
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Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.