Interstellar Weather Vanes: GLIMPSE Mid-Infrared Stellar-Wind Bowshocks in M17 and RCW49

TL;DR

This study reports the discovery of six infrared stellar-wind bowshocks in the star-forming regions M17 and RCW49 using Spitzer data, providing insights into stellar winds, dust heating, and gas flows in these regions.

Contribution

First identification of multiple infrared stellar-wind bowshocks in M17 and RCW49, with spectral analysis revealing properties of associated O stars and gas dynamics.

Findings

Six bowshocks discovered in M17 and RCW49

Spectral types of four O stars estimated

Evidence of large-scale gas flow from RCW49

Abstract

We report the discovery of six infrared stellar-wind bowshocks in the Galactic massive star formation regions M17 and RCW49 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 bowshocks. We combine Two Micron All-Sky Survey (2MASS), Spitzer, MSX, and IRAS observations to obtain the spectral energy distributions (SEDs) of the bowshocks and their individual driving stars. We use the stellar SEDs to estimate the spectral types of the three newly-identified O stars in RCW49 and one previously undiscovered O star in M17. One of the bowshocks in RCW49 reveals the presence of a large-scale flow of gas escaping the H II region at a few 10^2 km/s. Radiation-transfer modeling of the steep rise in the SED of this bowshock toward longer mid-infrared wavelengths indicates that the emission is coming principally from dust heated by the star driving the shock. The other 5 bowshocks occur where the stellar winds of O stars sweep up dust in the expanding H II regions.