Hierarchical Fragmentation of the Orion Molecular Filaments
Abstract
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.'5 × 2.'0 (0.88 × 0.27 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 (n_{H_2}≥ 10^6 cm-3), 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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 2013
- DOI:
- 10.1088/0004-637X/763/1/57
- arXiv:
- arXiv:1211.6842
- Bibcode:
- 2013ApJ...763...57T
- Keywords:
-
- ISM: clouds;
- ISM: individual objects: OMC-3 Orion A;
- ISM: structure;
- stars: formation;
- stars: protostars;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 35 pages, 5 figures, Accepted to ApJ