B68 – The HERSCHEL view Dust temperatures and densities B68 – The HERSCHEL view Dust temperatures and densities Markus Nielbock (MPIA) (Herschel PACS ICC) Ralf Launhardt, Jürgen Steinacker, Amy Stutz, Zoltan Balog, Henrik Beuther, Jeroen Bouwman, Thomas Henning, Pierre Hily-Blant, Jouni Kainulainen, Oliver Krause, Hendrik Linz, Nils Lippok, Sarah Ragan, Christophe Risacher, Anika Schmiedeke Markus Nielbock (MPIA) (Herschel PACS ICC) Ralf Launhardt, Jürgen Steinacker, Amy Stutz, Zoltan Balog, Henrik Beuther, Jeroen Bouwman, Thomas Henning, Pierre Hily-Blant, Jouni Kainulainen, Oliver Krause, Hendrik Linz, Nils Lippok, Sarah Ragan, Christophe Risacher, Anika Schmiedeke

EPoS – The Earliest Phases of Star formation Herschel guaranteed time key programme (PI: O. Krause, MPIA)Herschel guaranteed time key programme (PI: O. Krause, MPIA) to investigate well studied cloud cores across the entire mass rangeto investigate well studied cloud cores across the entire mass range to determine the dust temperature and density distribution of 12 near and isolatedto determine the dust temperature and density distribution of 12 near and isolated low-mass cores (Launhardt et al. 2012, in prep.; see also poster A05) used PACS and SPIRE bolometers at 100, 160, 250, 350, and 500 µmused PACS and SPIRE bolometers at 100, 160, 250, 350, and 500 µm added ground-based (sub)mm and NIR extinction dataadded ground-based (sub)mm and NIR extinction data this talk: results of the starless core B68 (Nielbock et al. 2012, in press; see poster A07)this talk: results of the starless core B68 (Nielbock et al. 2012, in press; see poster A07)

Barnard 68 B68B68 B71B71 B69B69 B70B70 B73B73 B74B74 B72B72

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

Continuum data

Ray-Tracing Modelling Results simple SED fitting affected by LoS temperature averagingsimple SED fitting affected by LoS temperature averaging employed 3D ray-tracing SED fitting (outside in)employed 3D ray-tracing SED fitting (outside in) assumed functional relationship for mean radial density profile (Plummer-like,assumed functional relationship for mean radial density profile (Plummer-like, e.g. Whitworth & Ward-Thompson 2001) externally heatedexternally heated T dust = 8 – 17 (20) K n H = (3.4 – 0.04) x 10 5 cm -3 T dust = 8 – 17 (20) K n H = (3.4 – 0.04) x 10 5 cm -3

Ray-Tracing Modelling Results radial distribution of temperature and densitiesradial distribution of temperature and densities flat central distributions steep slope in transition region  n H ~ 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

Core collision scenario Burkert & Alves (2009) B68B68 B71B71 B69B69 Alves et al. (2001)

Summary and conclusions observed the starless core B68 with the Herschel Space Telescopeobserved the starless core B68 with the Herschel Space Telescope resolved the distribution of the dust temperature and densityresolved 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 centrenegative 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)central density agrees with NIR extinction mapping results of Alves et al. (2001) steep slope of mean radial density profile between r = 1’ and 3’steep slope of mean radial density profile n H ~ r -3.5 between r = 1’ and 3’ contradicts SIS predictions, but agrees with filamentary origin or/and external pressurecontradicts SIS predictions, but agrees with filamentary origin or/and external pressure peculiar FIR morphology consistent with anisotropic radiation fieldpeculiar FIR morphology consistent with anisotropic radiation field ground-based CO observations are qualitatively consistent with core collision scenarioground-based CO observations are qualitatively consistent with core collision scenario Next steps: full 3D radiative transfer modellingfull 3D radiative transfer modelling exploit public Herschel data covering larger environment of B68exploit public Herschel data covering larger environment of B68

Anisotropic irradiation peculiar crescent-shaped morphology of FIR emission does not follow densitypeculiar crescent-shaped morphology of FIR emission does not follow density connected to (very uncertain) temperature gradient to SE?connected to (very uncertain) temperature gradient to SE? can be explained with irradiation by anisotropic external irradiation fieldcan be explained with irradiation by anisotropic external irradiation field 3D rad. transfer modelling3D rad. transfer modelling can reproduce shape qualitatively B68 40 pc above gal. planeB68 40 pc above gal. plane B2IV star  Oph nearbyB2IV star  Oph nearby