AAS 205th Meeting, 9-13 January 2005
Session 60 Secular Evolution Potpourri: Star Formation to Galactic Structures
Poster, Tuesday, January 11, 2005, 9:20am-6:30pm, Exhibit Hall

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[60.07] The Radial Distribution of the 8 micron Emission in Galaxies: Evidence for Secular Evolution

M. W. Regan (STScI), SINGS Team

The evolution of a galaxy is linked to its interstellar medium. The distribution of the ISM controls the amount and location of any star formation. If, over time, the ISM in the galaxy becomes more centrally concentrated than the stars, the radial distribution of the stars will also evolve to become more centrally concentrated. This process can form a psuedo-bulge and cause a galaxy to change its Hubble type. In this poster we present SPITZER IRAC radial profiles of 11 galaxies from SINGS. The radial profiles of the 3.5 micron channel are excellent tracers of the stellar content of the galaxies, while the 8 micron emission arises from PAH molecules that are good overall tracers of the ISM surface density. Our profiles reveal that many of the galaxies show an excess of emission in their central regions above the inner extrapolation of an exponential disk that is consistent with the expectations of secular evolution.

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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.