Science Highlights

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left: 850 μm continuum emission of the northern part of OMC-3 region including G208-N2 observed with the JCMT SCUBA-2 (Yi et al. 2018) in contours overlaid on the Hershel PACS 70 μm image in color. middle: 1.3 mm continuum emission from G208N2 observed with the ALMA. right: A close-up view of the 1.1 mm continuum emission.

The molecular cloud core G208.68-19.02-N2 (G208-N2) is located in the northern region of the Orion Molecular Cloud 3 (OMC-3), at the southern edge of the reflection nebula NGC 1977 in Orion's Sword. This core lies within a chain of molecular cloud cores delineated by 850-micron emission (contours in the left panel). The lack of 70-micron emission suggests that no protostar is currently embedded within the core. The ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP) project has observed the dust continuum emission from this core using the Atacama Large Millimeter/submillimeter Array (ALMA), revealing that the dense gas in this core exhibits a filamentary structure (shown in the middle panel). At the eastern tip of this filament, there is a compact object that resembles the "eye of a dragon" (depicted in both the middle and right panels). This compact object, which we refer to as the "nucleus," has a radius of approximately 150–200 AU, a mass of ~0.1 M⊙, and a central density of about 2 × 10⁹ cm⁻³. Based on a dynamical study, the nucleus appears to be gravitationally unstable. However, there is no evidence of protostellar activity, such as a molecular outflow, indicating that the object is not yet in the process of star formation. These observations suggest that the nucleus in G208-N2 is a prestellar core, potentially on the verge of forming a first hydrostatic core (FHSC) or may even be a candidate for FHSC. N. Hirano et al. (2024), ApJ, 961, 123