Dust, Ice, and Gas In Time (DIGIT) Herschel program first results. A full PACS-SED scan of the gas line emission in protostar DK Chamaeleontis
Waters, L. B. F. M.; Maret, S.; Güdel, M.; Dominik, C.; Henning, Th.; van Dishoeck, E. F.; Pontoppidan, K. M.; Evans, N. J.; Blake, G. A.; Merín, B.; Acke, B.; Olofsson, J.; Cieza, L.; Meeus, G.; Augereau, J. C.; Meijerink, R.; Kristensen, L. E.; Waelkens, C.; Lacy, J. H.; Hogerheijde, M. R.; Bouwman, J.; Dullemond, C. P.; Herczeg, G. J.; Bergin, E.; Jørgensen, J. K.; van Kempen, T. A.; Visser, R.; Yıldız, U. A.; Najita, J.; Lee, J. -E.; Knez, C.; Harvey, P. M.; Chen, J. -H.; Brown, J. M.; Mulders, G. D.; Salyk, C.; Kim, H. J.; Green, J. D.; Dunham, M. M.; Adamkovics, M.; Carr, J. S.; Glassgold, A.; Jaffe, D.; Mundy, L.; Sturm, B.
United States, Netherlands, Germany, Spain, South Korea, Denmark, Belgium, France, Austria
Abstract
Aims: We aim to study the composition and energetics of the circumstellar material of DK Cha, an intermediate-mass star in transition from an embedded configuration to a star plus disk stage, during this pivotal stage of its evolution.
Methods: Using the range scan mode of PACS on the Herschel Space Observatory, we obtained a spectrum of DK Cha from 55 to 210 μm as part of the DIGIT key program.
Results: Almost 50 molecular and atomic lines were detected, many more than the 7 lines detected in ISO-LWS. Nearly the entire ladder of CO from J = 14-13 to 38-37 (Eu/k = 4080 K), water from levels as excited as JK_{-1K+1} = 707 (Eu/k = 843 K), and OH lines up to Eu/k = 290 K were detected.
Conclusions: The continuum emission in our PACS SED scan matches the flux expected by a model consisting of a star, a surrounding disk of 0.03 M_⊙, and an envelope of a similar mass, supporting the suggestion that the object is emerging from its main accretion stage. Molecular, atomic, and ionic emission lines in the far-infrared reveal the outflow's influence on the envelope. The inferred hot gas may be photon-heated, but some emission may be caused by C-shocks in the walls of the outflow cavity.