What determines the density structure of molecular clouds? A case study of Orion B with Herschel

We present Herschel observations from the Herschel Gould Belt Survey and SCUBA-2 science verification observations from the JCMT Gould Belt Survey of the B1 clump in the Perseus molecular cloud. We determined the dust emissivity index using four different techniques to combine the Herschel PACS+SPIRE data at 160–500μm with the SCUBA-2 data at 450μm and 850μm. Of our four techniques, we found that the most robust method was filtering out the large-scale emission in the Herschel bands to match the spatial scales recovered by the SCUBA-2 reduction pipeline. Using this method, we find β ≈ 2 toward the filament region and moderately dense material and lower β values (β 1.6) toward the dense protostellar cores, possibly due to dust grain growth. We find that β and temperature are more robust with the inclusion of the SCUBA-2 data, improving estimates from Herschel data alone by factors of ∼2 for β and by ∼40% for temperature. Furthermore, we find core mass differences of 30% compared to Herschel-only estimates with an adopted β = 2, highlighting the necessity of long-wavelength submillimeter data for deriving accurate masses of prestellar and protostellar cores.