Infrared Photometric Properties of 709 Candidate Stellar Bowshock Nebulae

Abstract

Arcuate infrared nebulae are ubiquitous throughout the Galactic Plane and are candidates for partial shells, bubbles, or bowshocks produced by massive runaway stars. We tabulate infrared photometry for 709 such objects using images from the Spitzer Space Telescope (SST), Wide-Field Infrared Explorer (WISE), and Herschel Space Observatory (HSO). Of the 709 objects identified at 24 or 22 microns, 422 are detected at the HSO 70 micron bandpass. Of these, only 39 are detected at HSO 160 microns. The 70 micron peak surface brightnesses are 0.5 to 2.5 Jy/square arcminute. Color temperatures calculated from the 24 micron to 70 micron ratios range from 80 K to 400 K. Color temperatures from 70 micron to 160 micron ratios are systematically lower, 40 K to 200 K. Both of these temperature are, on average, 75% higher than the nominal temperatures derived by assuming that dust is in steady-state radiative equilibrium. This may be evidence of stellar wind bowshocks sweeping up and heating --- possibly fragmenting but not destroying --- interstellar dust. Infrared luminosity correlates with standoff distance, R_0, as predicted by published hydrodynamical models. Infrared spectral energy distributions are consistent with interstellar dust exposed to a either single radiant energy density, U=10^3 to 10^5 (in more than half of the objects) or a range of radiant energy densities U_min=25 to U_max=10^3 to 10^5 times the mean interstellar value for the remainder. Hence, the central OB stars dominate the energetics, making these enticing laboratories for testing dust models in constrained radiation environments. SEDs are consistent with PAH fractions q_PAH <1% in most objects.

Accepted for publication in the Astrophysical Journal

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