AAS 204th Meeting, June 2004
Session 41 Spitzer Space Telescope
Topical Related Poster, Tuesday, June 1, 2004, 10:00am-7:00pm, Ballroom

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[41.12] The Role of Photodissociation Regions in Massive Star Formation

J. L. Hora, L. E. Allen, S. T. Megeath, L. K. Deutsch, G. G Fazio (Harvard-Smithsonian Center for Astrophysics)

The evolution of high mass star formation regions is affected by the creation and evolution of photodissociation regions (PDRs), which are not present in the case of low mass star formation since stars in the latter do not emit the necessary UV. In star forming regions like AFGL 4029, NGC 7538 and S252, high mass YSOs representing a second generation of star formation are often found embedded in PDRs. Because of their proximity to HII regions, these clusters are also good laboratories for the study of ``sequential" or ``triggered" star formation, in which an expanding HII region compresses the molecular gas and induces star formation along the ionization front at the molecular cloud/HII region interface. In order to understand how the chemistry, composition, and structure of PDRs fit into the overall puzzle of high mass star formation, we have undertaken a program of IRAC imaging of the infrared emission from these regions. Three of IRAC's four bands include wavelengths of emission from PAHs, which are excellent diagnostics for probing the conditions in PDRs through spectral and spatial variations. We present the results from the IRAC images of the first objects in this survey, including a study of the PAH excitation in the PDRs, and an analysis of the young stars in these regions to determine whether their spatial distributions are consistent with the triggered star formation model.

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