Astrophys. J., 763, 57 (2013/January-3)
Hierarchical fragmentation of the Orion molecular filaments.
TAKAHASHI S., HO P.T.P., TEIXEIRA P.S., ZAPATA L.A. and SU Y.-N.
Abstract (from CDS):
We present a high angular resolution map of the 850 µm continuum emission of the Orion Molecular Cloud-3 (OMC 3) obtained with the Submillimeter Array (SMA); the map is a mosaic of 85 pointings covering an approximate area of 6.'5x2.'0 (0.88x0.27 pc). We detect 12 spatially resolved continuum sources, each with an H2 mass between 0.3-5.7 M☉and a projected source size between 1400-8200 AU. All the detected sources are on the filamentary main ridge (nH2 ≥ 106/cm3), and analysis based on the Jeans theorem suggests that they are most likely gravitationally unstable. Comparison of multi-wavelength data sets indicates that of the continuum sources, 6/12 (50%) are associated with molecular outflows, 8/12 (67%) are associated with infrared sources, and 3/12 (25%) are associated with ionized jets. The evolutionary status of these sources ranges from prestellar cores to protostar phase, confirming that OMC-3 is an active region with ongoing embedded star formation. We detect quasi-periodical separations between the OMC-3 sources of ~17''/0.035 pc. This spatial distribution is part of a large hierarchical structure that also includes fragmentation scales of giant molecular cloud (~35 pc), large-scale clumps (~1.3 pc), and small-scale clumps (~0.3 pc), suggesting that hierarchical fragmentation operates within the Orion A molecular cloud. The fragmentation spacings are roughly consistent with the thermal fragmentation length in large-scale clumps, while for small-scale cores it is smaller than the local fragmentation length. These smaller spacings observed with the SMA can be explained by either a helical magnetic field, cloud rotation, or/and global filament collapse. Finally, possible evidence for sequential fragmentation is suggested in the northern part of the OMC-3 filament.
ISM: clouds - ISM: individual (OMC-3, Orion A) - ISM: structure - stars: formation - stars: protostars
Table 3: [THT2013] OMC3-SMM NN (Nos 1-12)
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