Aug 2012: New Star Neighborhoods
Cornell undergrad, Lea Hirsch, and, Research Associate, Joe Adams discuss their recent paper:
"SOFIA/FORCAST and Spitzer/IRAC Imaging of the Ultra Compact H II Region W3(OH) and Associated Protostars in W3" by L. Hirsch, J. Adams, T. Herter, J. Hora, et al.
Ultra-compact HII (UCHII) regions are very small regions of space in which the normally neutral hydrogen gas in the interstellar medium is ionized by the radiation from a newly formed massive star. Thus, studying ultra-compact HII regions allows us to probe the environments of recent massive star formation. In our paper, we examined "W3(OH)", an UCHII region 2 kpc away in the W3 giant molecular cloud, using data taken by Cornell’s FORCAST instrument aboard SOFIA, and the Spitzer Space Telescope’s IRAC camera.
A dust shell surrounds the HII region, that absorbs ultraviolet and visible light but re-radiates that energy in the infrared. We contribute new, high resolution measurements of W3(OH) at 3 – 37 microns, IR wavelengths critical for understanding the luminosity of the star. With SOFIA’s high spatial resolution, we were able to measure the precise diameter of the dust shell (60,000 AU). Combining our data with data from the 2MASS catalogue and other sources in the literature, we produce the well-sampled spectral energy distribution (power as a function of wavelength) shown in the figure. We used this to model the properties of the dust: its optical depth, temperature, and the distribution of grain sizes. What is more, the dust is clumpy, allowing radiation from the hotter interior to shine through.
We also provide the first spatially resolved infrared observations of the nearby water maser source, W3(H2O) and examined four nearby intermediate- and high-luminosity young stars containing circumstellar envelopes and/or disks.