We present infrared observations of the ultra-compact H II region W3(OH) made by the FORCAST instrument aboard SOFIA and by Spitzer/IRAC. We contribute new wavelength data to the spectral energy distribution, which constrains the optical depth, grain
size distribution, and temperature gradient of the dusty shell surrounding the H II region. We model the dust component as a spherical shell containing an inner cavity with radius ~ 600 AU, irradiated by a central star of type O9 and temperature ~ 31,000 K. The total luminosity of this system is 71,000 L_solar. An observed excess of 2.2 - 4.5 microns emission in the SED can be explained by our viewing a cavity opening or clumpiness in the shell structure whereby radiation from the warm interior of the shell can escape. We claim to detect the nearby water maser source W3 (H2O) at 31.4 and 37.1 microns using beam deconvolution of the FORCAST images. We constrain the flux densities of this object at 19.7 - 37.1 microns. Additionally, we present in situ observations of four young stellar and protostellar objects in the SOFIA field, presumably associated with the W3 molecular cloud. Results from the model SED fitting tool of Robitaille et al. (2006, 2007} suggest that two objects (2MASS J02270352+6152357 and 2MASS J02270824+6152281) are intermediate-luminosity (~ 236 - 432 L_solar) protostars; one object (2MASS J02270887+6152344) is either a high-mass protostar with luminosity 3000 L_solar or a less massive young star with a substantial circumstellar disk but depleted envelope; and one object (2MASS J02270743+6152281) is an intermediate-luminosity (~ 768 L_solar) protostar nearing the end of its envelope accretion phase or a young star surrounded by a circumstellar disk with no appreciable circumstellar envelope.
We present new mid-infrared images of the central region of the Orion Nebula using the newly commissioned SOFIA airborne telescope and its 5 -- 40 micron camera FORCAST. The 37.1 micron images represent the highest resolution observations (<4) ever o
btained of this region at these wavelengths. After BN/KL (which is described in a separate letter in this issue), the dominant source at all wavelengths except 37.1 micron is the Ney-Allen Nebula, a crescent-shaped extended source associated with theta 1D. The morphology of the Ney-Allen nebula in our images is consistent with the interpretation that it is ambient dust swept up by the stellar wind from theta 1D, as suggested by Smith et al. (2005). Our observations also reveal emission from two proplyds (proto-planetary disks), and a few embedded young stellar objects (YSOs; IRc9, and OMC1S IRS1, 2, and 10). The spectral energy distribution for IRc9 is presented and fitted with standard YSO models from Robitaille et al. (2007) to constrain the total luminosity, disk size, and envelope size. The diffuse, nebular emission we observe at all FORCAST wavelengths is most likely from the background photodissociation region (PDR) and shows structure that coincides roughly with H_alpha and [N II] emission. We conclude that the spatial variations in the diffuse emission are likely due to undulations in the surface of the background PDR.
We present 37micron imaging of the S140 complex of infrared sources centered on IRS1 made with the FORCAST camera on SOFIA. These observations are the longest wavelength imaging to resolve clearly the three main sources seen at shorter wavelengths, I
RS 1, 2 and 3, and are nearly at the diffraction limit of the 2.5-m telescope. We also obtained a small number of images at 11 and 31micron that are useful for flux measurement. Our images cover the area of several strong sub-mm sources seen in the area -- SMM 1, 2, and 3 -- that are not coincident with any mid-infrared sources and are not visible in our longer wavelength imaging either. Our new observations confirm previous estimates of the relative dust optical depth and source luminosity for the components in this likely cluster of early B stars. We also investigate the use of super-resolution to go beyond the basic diffraction limit in imaging on SOFIA and find that the van Cittert algorithm, together with the multi-resolution technique, provides excellent results.
