Volume 553, May 2013
|Number of page(s)||13|
|Section||Interstellar and circumstellar matter|
|Published online||16 May 2013|
SABOCA 350-μm and LABOCA 870-μm dust continuum imaging of IRAS 05399-0121: mapping the dust properties of a pre- and protostellar core system⋆
1 Department of Physics, University of Helsinki, PO Box 64, 00014 Helsinki, Finland
2 Department of Astronomy, Yale University, New Haven, CT 06511, USA
Received: 14 February 2013
Accepted: 25 March 2013
Context. Thermal emission from dust provides a valuable tool for determining important physical properties of the dense structures within molecular clouds.
Aims. We attempt to map the distributions of dust temperature and H2 column density of IRAS 05399-0121/SMM 1, which is a dense double-core system in Orion B9. We also search for substructures within the cores through high-resolution submillimetre imaging.
Methods. The source was mapped with APEX/SABOCA at 350 μm. We combined these data with our previous LABOCA 870-μm data. The spatial resolution of the new SABOCA image, ~3400 AU, is about 2.6 times better than provided by LABOCA, and is therefore well-suited to our purposes. We also make use of the Spitzer infrared observations to characterise the star-formation activity in the source.
Results. The filamentary source remains a double-core system on the 3400 AU scale probed here, and the projected separation between IRAS 05399 and SMM 1 is 0.14 pc. The temperature map reveals warm spots towards IRAS 05399 and the southeastern tip of the source. Both IRAS 05399 and SMM 1 stand out as peaks in the column density map. A simple analysis suggests that the density profile has the form ~r-(2.3-0.9+2.2), as determined at the position of SMM 1. The broadband spectral energy distribution of IRAS 05399 suggests that it is near the Stage 0/I borderline. A visual inspection of the Spitzer/IRAC images provides hints of a quadrupolar-like jet morphology around IRAS 05399, supporting the possibility that it is a binary system.
Conclusions. The source splitting into two subcores along the long axis can be explained by cylindrical Jeans-type fragmentation, but the steepness of the density profile is shallower than what is expected for an isothermal cylinder. The difference between the evolutionary stages of IRAS 05399 (protostellar) and SMM 1 (starless) suggests that the former has experienced a phase of rapid mass accretion, supported by the very long outflow it drives. The protostellar jet from IRAS 05399 might have influenced the nearby core SMM 1. In particular, the temperature map features are likely to be imprints of protostellar or shock heating, while external heating could be provided by the nearby high-mass star-forming region NGC 2024.
Key words: stars: formation / stars: protostars / ISM: individual objects: IRAS 05399-0121 / submillimeter: ISM
This publication is based on data acquired with the Atacama Pathfinder EXperiment (APEX) under programmes 079.F-9313(A) and 090.F-9307(A). APEX is a collaboration between the Max-Planck-Institut für Radioastronomie, the European Southern Observatory, and the Onsala Space Observatory.
© ESO, 2013
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