Volume 569, September 2014
|Number of page(s)||11|
|Section||Interstellar and circumstellar matter|
|Published online||10 September 2014|
The Earliest Phases of Star formation (EPoS)
Temperature, density, and kinematic structure of the star-forming core CB 17⋆
Leiden Observatory, Leiden University,
PO Box 9513,
2 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
3 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
4 Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
Accepted: 25 May 2014
Context. The initial conditions for the gravitational collapse of molecular cloud cores and the subsequent birth of stars are still not well constrained. The characteristic cold temperatures (~10 K) in such regions require observations at sub-millimetre and longer wavelengths. The Herschel Space Observatory and complementary ground-based observations presented in this paper have the unprecedented potential to reveal the structure and kinematics of a prototypical core region at the onset of stellar birth.
Aims. This paper aims to determine the density, temperature, and velocity structure of the star-forming Bok globule CB 17. This isolated region is known to host (at least) two sources at different evolutionary stages: a dense core, SMM1, and a Class I protostar, IRS.
Methods. We modeled the cold dust emission maps from 100 μm to 1.2 mm with both a modified blackbody technique to determine the optical depth-weighted line-of-sight temperature and column density and a ray-tracing technique to determine the core temperature and volume density structure. Furthermore, we analysed the kinematics of CB17 using the high-density gas tracer N2H+.
Results. From the ray-tracing analysis, we find a temperature in the centre of SMM1 of T0 = 10.6 K, a flat density profile with radius 9.5 × 103 au, and a central volume density of nH,0 = 2.3 × 105 cm-3. The velocity structure of the N2H+ observations reveal global rotation with a velocity gradient of 4.3 km s-1 pc-1. Superposed on this rotation signature we find a more complex velocity field, which may be indicative of differential motions within the dense core.
Conclusions. SMM is a core in an early evolutionary stage at the verge of being bound, but the question of whether it is a starless or a protostellar core remains unanswered.
Key words: dust, extinction / ISM: molecules / ISM: kinematics and dynamics / stars: formation / stars: low-mass / ISM: individual objects: CB 17
The Herschel data (Fig. 2) including N- and T-maps in Fig. 3 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/569/A7
© ESO, 2014
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