Volume 383, Number 2, FebruaryIV 2002
|Page(s)||502 - 518|
|Section||Interstellar and circumstellar matter|
|Published online||15 February 2002|
Active star formation in the large Bok globule CB 34*
Armagh Observatory, Armagh BT61 9DG, Northern Ireland, UK e-mail: firstname.lastname@example.org
2 Centro Astronomico Hispano-Aleman, 04080 Almeria, Spain e-mail: email@example.com
3 MPI für Radioastronomie, Auf dem Hügel 69, 53121, Bonn, Germany e-mail: firstname.lastname@example.org
4 Joint Astronomy Centre 660 N. A'Ohoku Place, University Park, Hilo, Hawaii 96720, USA e-mail: email@example.com
Corresponding author: T. Khanzadyan, firstname.lastname@example.org
Accepted: 29 October 2001
We present near-infrared and millimetre observations of the large Bok globule CB 34. Two long parallel trails of H2 knots are discovered on wide-field images in the 1–0 S(1) 2.12 μm emission line. These parsec scale H2 jets extend to the edge of the dark globule where they disappear without the trace of bow shocks. This suggests that the outflows physically extend into a lower density ambient medium where their terminating bows are beyond present detection limits. The two outflows are extremely well collimated and parallel to within 3°. The outflow mechanical luminosity, derived from CO measurements, and the shocked luminosity, estimated from the H2 emission, are similar, consistent with jet-driven non-evolving outflow structure. The jets appear to originate from the densest cores, as observed in H13CO+ line emission. A central concentration of reddened stars and a lower density halo of less reddened stars within the globule are revealed by JHK photometry. Disordered motions are observed in the CO line velocity channel maps and can be driven by the power of the outflows emanating from dense cores. We sketch a picture for the star formation history of the globule in which two star phases have been formed. A weak diffuse emission halo is detected in the near infrared with colours consistent with either scattered light or a ro-vibrational H2 cascade. We propose that the halo is produced by ongoing H2 formation. Cloud evolution and halo H2 formation timescales are then both a few 105 yr. Thus, we may be witnessing the formation of a molecular cloud out of diffuse atomic gas. This supports a scheme in which this Bok globule has formed independently rather than through dislocation from a nearby molecular cloud.
Key words: infrared: ISM / stars: formation / ISM: jets and outflows / ISM: clouds
© ESO, 2002
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