SOFIA-FORCAST Imaging of Giant HII Regions in Our Galaxy

We know very little about clustered star formation in comparison to isolated star formation, even though it is believed that most stars form in OB clusters. Giant HII (GHII) regions host the most active areas of OB star formation in the galaxy, and as such are great laboratories for the study of the earliest stages of clustered star formation. An understanding of the link between the large unresolved star forming regions which dominate in external galaxies, require the results from a holistic study like this one of similar regions in our own Galaxy to calibrate their properties. This study uses SOFIA's FORCAST instrument to collect 19.7 um and 37.1 um maps of all 56 GHII regions in the Milky Way, and 8 targets have been observed so far. The 37um maps have the best-ever achieved resolution at that wavelength. The combination of longer wavelength IR data and good spatial resolution allow the detection and characterization of embedded young stellar objects and the colder dust population throughout the GHII regions. These data are being combined with Spitzer/IRAC, Herschel 70 um, and radio (2-6 cm) data already collected for these targets to determine the physical properties of the dust, including dust mass, temperature, and optical depth, derived across the GHII regions.