2008ApJ...689..242P

We report the discovery of six infrared stellar wind bow shocks in the Galactic massive star formation regions M17 and RCW 49 from Spitzer GLIMPSE (Galactic Legacy Infrared Mid-Plane Survey Extraordinaire) images. The Infrared Array Camera (IRAC) on the Spitzer Space Telescope clearly resolves the arc-shaped emission produced by the bow shocks. We combine Two Micron All-Sky Survey (2MASS), Spitzer, MSX, and IRAS observations to obtain the spectral energy distributions (SEDs) of the bow shocks and their individual driving stars. We use the stellar SEDs to estimate the spectral types of the three newly identified O stars in RCW 49 and one previously undiscovered O star in M17. One of the bow shocks in RCW 49 reveals the presence of a large-scale flow of gas escaping the H II region at a few 10² km/s. Radiation transfer modeling of the steep rise in the SED of this bow shock toward longer mid-infrared wavelengths indicates that the emission is coming principally from dust heated by the star driving the shock. The other five bow shocks occur where the stellar winds of O stars sweep up dust in the expanding H II regions.