Dissection of the protostellar envelope surrounding IRAS 05173-0555 in L1634

Astronomy and Astrophysics (Impact Factor: 4.48). 03/2008; DOI: 10.1051/0004-6361:20079224
Source: arXiv

ABSTRACT Context. The youngest protostars that power energetic outflows are surrounded by infalling and rotating envelopes that contain most of the mass of the system. Aims. To study the properties and kinematics of the protostellar envelope surrounding the embedded source IRAS 05173-0555 in L1634. Methods. We carried out VLA ammonia observations at 1.3 cm with the VLA in the D configuration to map the gas towards the core of L1634. Results. The NH3 emission towards IRAS 05173-0555 is resolved and shows two components clearly distinguishable morphologically: a cross-like structure, roughly elongated in the direction of the HH 240/241 outflow and associated with IRAS 05173-0555, plus an arc-like stream elongated towards the north. The properties and kinematics of the gas suggest that the origin of the cross-like morphology could be the interaction between the outflow and the envelope. A more compact and flattened structure, which could be undergoing rotation about the axis of the outflow, has been detected towards the center of the cross-like envelope. The northern stream, which has properties and velocity different from those of the cross-like envelope, is likely part of the original cloud envelope, and could be either a quiescent core that would never form stars, or be in a prestellar phase. Comment: 10 pages, 9 figures, accepted for publication in A&A

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    ABSTRACT: Bright-rimmed clouds (BRCs) appear to be sites of triggered star formation induced through the propagation of shocks initiated by the expansion of nearby H ii regions. Our main aim is to establish support for observations of star-forming activity within a sample of BRCs. A secondary aim is to establish a plausible link between such star formation and observed external influences. We have conducted CO (J = 2–1) observations using the James Clerk Maxwell Telescope to probe the environments of a sample of star-forming BRCs associated with embedded protostellar cores. Local thermodynamic equilibrium analysis allows the determination of the physical properties of these protostars and investigation of the structure and kinematic motions within the molecular gas. Using a combination of archival radio and mid-infrared data, and submillimeter observations, we have refined the Sugitani, Fukui and Ogura (SFO) catalogue, excluding 18 BRCs that do not show any evidence of photoionization induced collapse. Of the remaining 26 clouds that are being photoionized, we find 20 that are associated with embedded protostars. These 20 clouds are excellent candidates with which to further investigate the radiatively driven implosion mode of triggered star formation. Comparing the physical parameters of the triggered and untriggered samples, we find that the surface temperatures of the potentially triggered clouds are significantly higher (by ∼10 K) than those in which triggering is considered unlikely. The higher surface temperatures found towards the sample of potentially triggered clouds are consistent with the hypothesis that these clouds are being externally heated through their exposure to the H ii region.
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