Matthew S. Povich Research
Two Galactic H II regions compared. The bubble N49 (Churchwell et al. 2006, Watson et al. 2008) appears to have been blown by a single, hot, early O-type star (diamond). The star is surrounded by concentric zones of distinct emission: An interior shell of ionized gas seen in radio emission (contours) also contains warm dust emitting in the IR at 24 microns (red), and the exterior rim of the bubble is defined by 8 micron IR emission (green) from complex organic molecules (a.k.a. polycyclic aromatic hydrocarbons, or PAHs). The giant H II region M17, by contrast, is powered by more than a dozen early O-type stars (diamonds). M17 exhibits a much more complicated structure than N49, but the same basic emission zones can be discerned using a similar color coding for both images (note the physical size scales are matched, too). The major difference is M17’s inner zone of very hot (10 MK) plasma, which emits soft X-rays (blue). Both the large, central cavity in the M17 nebula and the hot plasma filling. N49 has a much smaller central cavity (the “donut hole” in the 24 micron emission), and so far no observation has looked for X-rays there.