On the Nature of the Deeply Embedded Protostar Omc-2 Fir 4

We use mid-infrared to submillimeter data from the Spitzer, Herschel, and APEX telescopes to study the bright sub-mm source OMC-2 FIR 4. We find a point source at 8, 24, and 70 μm, and a compact, but extended source at 160, 350, and 870 μm. The peak of the emission from 8 to 70 μm, attributed to the protostar associated with FIR 4, is displaced relative to the peak of the extended emission; the latter represents the large molecular core the protostar is embedded within. We determine that the protostar has a bolometric luminosity of 37 L⊙, although including more extended emission surrounding the point source raises this value to 86 L⊙. Radiative transfer models of the protostellar system fit the observed SED well and yield a total luminosity of most likely less than 100 L⊙. Our models suggest that the bolometric luminosity of the protostar could be just 12-14 L⊙, while the luminosity of the colder (∼ 20 K) extended core could be around 100 L⊙, with a mass of about 27 M⊙. Our derived luminosities for the protostar OMC-2 FIR 4 are in direct contradiction with previous claims of a total luminosity of 1000 L⊙ (Crimier et al. 2009). Furthermore, we find evidence from farinfrared molecular spectra (Kama et al. 2013; Manoj et al. 2013) and 3.6 cm emission (Reipurth et al. 1999) that FIR 4 drives an outflow. The final stellar mass the protostar will ultimately achieve is uncertain due to its association with the large reservoir of mass found in the cold core. Subject headings: circumstellar matter — infrared: stars — stars: formation — stars: individual (OMC-2 FIR 4) — stars: protostars