Protostellar condensations in the core of NGC 2024

Abstract

The J = 4-3 transition of HCO(+) was observed in the core of NGC 2024. The findings indicate a possibly expanding torus centered around the FIR 6 continuum source and an E-W ridge below the ionization front. The presence of HCO(+) J = 4-3 emission from the torus and E-W ridge suggests relatively high gas densities in these regions. The relatively strong intensity of the observed HCO(+) J = 4-3 emission toward the FIR source suggests that the emission originates from relatively warm and dense gas. Continuum radiation transport modeling of the core shows that submillimeter and millimeter continuum observations of the cores can be reproduced under the assumption that the cores are externally heated objects without internal heating sources. This requires a factor of about 250 enhancement of the external radiation field intensity compared to the standard Galactic radiation field. This enhancement is consistent with the stellar luminosities required to explain the observed FIR continuum emission from the region.