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B68 – The HERSCHEL view Dust temperatures and densities

B68 – The HERSCHEL view Dust temperatures and densities. Markus Nielbock

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B68 – The HERSCHEL view Dust temperatures and densities

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  1. B68 – The HERSCHEL view Dust temperatures and densities Markus Nielbock Ralf Launhardt, Jürgen Steinacker, Amy Stutz, ZoltanBalog, HenrikBeuther, JeroenBouwman, Thomas Henning, Pierre Hily-Blant, JouniKainulainen, Oliver Krause, Hendrik Linz, Nils Lippok, Sarah Ragan, Christophe Risacher, AnikaSchmiedeke

  2. EPoS– The Earliest Phases of Star formation • Herschel guaranteed time key programme (PI: O. Krause, MPIA) • to investigate well studied cloud cores across the entire mass range • to determine the dust temperature and density distribution of 12 near and isolated • low-mass cores (Launhardt et al. 2012, submitted) • used PACS and SPIRE bolometers at 100, 160, 250, 350, and 500 µm • added ground-based (sub)mm and NIR extinction data • this talk: results of the starless core B68(Nielbock et al. 2012, A&A, 547, A11)

  3. Barnard 68 B72 B68 B69 B70 B71 B74 B73

  4. Barnard 68 • starless core • distance:  150 pc • mass:  3 M • size:  0.2 pc (40 000 AU) • pre-stellar? • possibly on the verge of collapse Alves et al. (2001) Bonnor-Ebert fit NIR extinction

  5. Continuum data

  6. Ray-Tracing Modelling Results • simple SED fitting affected by LoS temperature averaging • employed 3D ray-tracing SED fitting (outside in) • assumed functional relationship for mean radial density profile parameterisation(Plummer-like, e.g. Whitworth & Ward-Thompson 2001) • externally heated • Tdust = 8 – 17 (20) K nH = (3.4  0.04) x 105 cm-3

  7. Ray-Tracing Modelling Results • radial distribution of temperature and densities • flat central distributions • steep slope in transition region • nH ~ r-3.5 • filamentary origin? (Ostriker 1964) • strong spatial variations r > 1’ • spheroid assumption invalid there • density drops to a flat distribution of the ambient tenous medium

  8. Anisotropic irradiation • peculiar crescent-shaped morphology of FIR emission does not follow density • connected to (very uncertain) temperature gradient to SE? • can be explained with irradiation by anisotropic external irradiation field • 3D rad. transfer modelling • can reproduce shape • qualitatively • B68 40 pc above gal. plane • B2IV star  Ophnearby

  9. Summary and conclusions • observed the starless core B68 with the Herschel Space Telescope • resolved the distribution of the dust temperature and density • negative temperature gradient from up to 20 K at the outskirts to 8 K in the core centre • central density agrees with NIR extinction mapping results of Alves et al. (2001) • steep slope of mean radial density profile nH ~ r-3.5between r = 1’ and 3’ • contradicts SIS predictions, but agrees with filamentary origin or/and external pressure • peculiar FIR morphology consistent with anisotropic radiation field • ground-based CO observations are qualitatively consistent with core collision scenario • Next steps: • full 3Dradiative transfer modelling • investigate origin of irradiation by studying scattered light • exploit public Herschel data covering larger environment of B68

  10. The Neighbourhood of B68 with Herschel ~50’ PACS 160 µm PACS 70 µm PACS 100 µm SPIRE 500 µm SPIRE 250 µm SPIRE 350 µm (Public) data of P. André’s Herschel KP “Gould’s Belt Survey”

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