Confirmation of Enhanced Long Wavelength Dust Emission in OMC 2/3

Previous continuum observations from the MUSTANG camera on the Green Bank Telescope (GBT) of the nearby star-forming filament OMC 2/3 found elevated emission at 3.3mm relative to shorter wavelength data. As a consequence, the inferred dust emissivity index obtained from modified black body dust spectra was considerably lower than what is typically measured on $\sim 0.1 pc$ scales in nearby molecular clouds. Here we present new observations of OMC 2/3 collected with the MUSTANG-2 camera on the GBT which confirm this elevated emission. We also present for the first time sensitive 1~cm observations made with the Ka-band receiver on the GBT which also show higher than expected emission. We use these observations--- along with Herschel, JCMT, Mambo, and GISMO data--- to assemble spectral energy distributions (SEDs) of a variety of structures in OMC 2/3 spanning the range $160 \mu m$ to $1 cm$. The data at 2mm and shorter are generally consistent with a modified black body spectrum and a single value of $\beta \sim 1.7$. The 3mm and 1cm data, however, lie well above such an SED. The spectrum of the long wavelength excess is inconsistent with both free-free emission and standard `Spinning Dust' models for Anomalous Microwave Emission. The 3mm and 1cm data could be explained by a much flatter dust spectrum, corresponding to $\beta \sim 0.7$, at wavelengths shorter than 2mm.