SOFIA {\it FORCAST} Photometry of 12 Extended Green Objects in the Milky Way

Massive young stellar objects are known to undergo an evolutionary phase in which high mass accretion rates drive strong outflows. A class of objects believed to trace this phase accurately is the GLIMPSE Extended Green Object (EGO) sample, so named for the presence of extended 4.5 $\mu$m emission on sizescales of $\sim$0.1 pc in $\mathit{\text{Spitzer}}$ images. We have been conducting a multi-wavelength examination of a sample of 12 EGOs with distances of 1 to 5 kpc. In this paper, we present mid-infrared images and photometry of these EGOs obtained with the SOFIA telescope, and subsequently construct SEDs for these sources from the near-IR to sub-millimeter regimes using additional archival data. We compare the results from greybody models and several publicly-available software packages which produce model SEDs in the context of a single massive protostar. The models yield typical \rstar/$\sim$10 \rsun, \tstar/$\sim$10${}^3$ to 10${}^4$ K, and \lstar/$\sim$1~$-$~40~$\times$~10${}^3$ \lsun; the median $L\mathrm{/}M$ for our sample is 24.7 \lsun/\msun. Model results rarely converge for \rstar/ and \tstar, but do for \lstar, which we take to be an indication of the multiplicity and inherently clustered nature of these sources even though, typically, only a single source dominates in the mid-infrared. The median $L\mathrm{/}M$ value for the sample suggests that these objects may be in a transitional stage between the commonly described IR-quiet'' and IR-bright’’ stages of MYSO evolution. The median $T_{dust}$ for the sample is less conclusive, but suggests that these objects are either in this transitional stage or occupy the cooler (and presumably younger) part of the IR-bright stage.