Volume 577, May 2015
|Number of page(s)||6|
|Published online||12 May 2015|
Nascent bipolar outflows associated with the first hydrostatic core candidates Barnard 1b-N and 1b-S⋆,⋆⋆,⋆⋆⋆
1 LERMA, Observatoire de Paris, CNRS UMR 8112, École Normale Supérieure, PSL research university, 24 rue Lhomond, 75231 Paris Cedex 05, France
2 Sorbonne Universités, , UPMC université Paris 06, 75000 Paris, France
3 Institut de Radioastronomie Millimétrique (IRAM), 300 rue de la Piscine, 38406 Saint-Martin d’ Hères, France
4 Observatorio Astronómico Nacional (OAN, IGN), Apdo 112, 28803 Alcalá de Henares, Spain
5 Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), 28049, Cantoblanco, Madrid, Spain
6 Centre de Recherche Astronomique de Lyon (CRAL), École Normale Supérieure de Lyon, CNRS-UMR 5574, 69364 Lyon Cedex 07, France
7 INAF, Istituto di Radioastronomia, via P. Gobetti 101, 40129 Bologna, Italy
Received: 31 January 2015
Accepted: 14 April 2015
In the theory of star formation, the first hydrostatic core (FHSC) phase is a critical step in which a condensed object emerges from a prestellar core. This step lasts about one thousand years, a very short time compared with the lifetime of prestellar cores, and therefore is hard to detect unambiguously. We present IRAM Plateau de Bure observations of the Barnard 1b dense molecular core, combining detections of H2CO and CH3OH spectral lines and dust continuum at 2.3′′ resolution (~500 AU). The two compact cores B1b-N and B1b-S are detected in the dust continuum at 2 mm, with fluxes that agree with their spectral energy distribution. Molecular outflows associated with both cores are detected. They are inclined relative to the direction of the magnetic field, in agreement with predictions of collapse in turbulent and magnetized gas with a ratio of mass to magnetic flux somewhat higher than the critical value, μ ~ 2−7. The outflow associated with B1b-S presents sharp spatial structures, with ejection velocities of up to ~7 km s-1 from the mean velocity. Its dynamical age is estimated to be ~2000 yr. The B1b-N outflow is smaller and slower, with a short dynamical age of ~1000 yr. The B1b-N outflow mass, mass-loss rate, and mechanical luminosity agree well with theoretical predictions of FHSC. These observations confirm the early evolutionary stage of B1b-N and the slightly more evolved stage of B1b-S.
Key words: ISM: clouds / ISM: jets and outflows / ISM: individual objects: Barnard 1b / stars: formation
Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).
Appendices are available in electronic form at http://www.aanda.org
FITS files for the H2CO and CH3OH mosaics are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (126.96.36.199) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/577/L2
© ESO, 2015
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