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

## TL;DR

This study confirms elevated long-wavelength dust emission in OMC 2/3, challenging standard models and suggesting a flatter dust emissivity spectrum or anomalous microwave emission as possible explanations.

## Contribution

First comprehensive multi-wavelength analysis of OMC 2/3 confirming elevated long-wavelength dust emission and exploring its origin.

## Key findings

- Elevated emission at 3 mm and 1 cm wavelengths in OMC 2/3.
- Standard dust models with β ~ 1.6 do not fit long-wavelength data.
- The excess emission cannot be explained by free-free or typical spinning dust models.

## Abstract

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 3.3 mm 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 $\sim 0.1 \, {\rm pc}$ 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 $160 \, {\rm \mu m}$ to $1 \, {\rm cm}$. The data at 2 mm and shorter are generally consistent with a modified black body spectrum and a single value of $\beta \sim 1.6$. The 3 mm and 1 cm 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 (AME). The 3 mm and 1 cm data could be explained by a flatter dust emissivity at wavelengths shorter than 2 mm, potentially in concert with AME in some regions.