High-Velocity Interstellar Bullets in IRAS05506+2414: A Very Young Protostar

Abstract

We have made a serendipitous discovery of an enigmatic outflow source, IRAS 05506+2414 (hereafter IRAS 05506), as part of a multi-wavelength survey of pre-planetary nebulae (PPNs). The HST optical and near-infrared images show a bright compact central source with a jet-like extension, and a fan-like spray of high-velocity (with radial velocities upto 350 kms/s) elongated knots which appear to emanate from it. These structures are possibly analogous to the near-IR "bullets" seen in the Orion nebula. Interferometric observations at 2.6 mm show the presence of a high-velocity CO outflow and a continuum source also with a faint extension, both of which are aligned with the optical jet structure. IRAS 05506 is most likely not a PPN. We find extended NH3 (1,1) emission towards IRAS 05506; these data together with the combined presence of far-IR emission, H2O and OH masers, and CO and CS J=2-1 emission, strongly argue for a dense, dusty star-forming core associated with IRAS 05506. IRAS 05506 is probably an intermediate-mass or massive protostar, and the very short time-scale (200 yr) of its outflows indicates that it is very young. If IRAS 05506 is a massive star, then the lack of radio continuum and the late G -- early K spectral type we find from our optical spectra implies that in this object we are witnessing the earliest stages of its life, while its temperature is still too low to provide sufficient UV flux for ionisation.

arXiv comment33 pages, 11 figures Accepted by The Astrophysical Journal (Feb 7, 2008)

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• Echelle long-slit optical spectroscopy of evolved stars
• Bipolar Planetary Nebulae from Outflow Collimation by Common Envelope Evolution
• The Orion Fingers: Near-IR Adaptive Optics Imaging of an Explosive Protostellar Outflow
• The Orion fingers: Near-IR spectral imaging of an explosive outflow
• YSO jets in the Galactic Plane from UWISH2: V - Jets and Outflows in M17
• IRAS 19520+2759: a 10^5 Lsun massive young stellar object driving a collimated outflow
• The Orion fingers: H${}_2$ temperatures and excitation in an explosive outflow
• An infrared study of Galactic OH/IR stars. III. Variability properties of the Arecibo sample
• A molecular-line study of the interstellar bullet engine IRAS 05506+2414
• Formation of Orion Fingers