Protostars and Planets VI, Heidelberg, July 15-20, 2013

Poster 1K056

High-velocity clumps in the L1157 outflow

Benedettini, Milena (INAF - Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy)
Viti, Serena (Department of Physics and Astronomy, University College London, London, UK)
Codella, Claudio (INAF - Osservatorio Astrofisico di Arcetri, Firenze, Italy)
Gueth, Frederic (Institut de Radio Astronomie Millimetrique, Saint Martin d\'Heres, France)
Gomez-Ruiz, Arturo (INAF - Osservatorio Astrofisico di Arcetri, Firenze, Italy)
Bachiller, Rafael (Observatorio Astronomico Nacional (IGN), Madrid, Spain)
Beltran, Maria (INAF - Osservatorio Astrofisico di Arcetri, Firenze, Italy)
Busquet, Gemma (INAF - Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy)
Ceccarelli, Cecilia (UJF-Grenoble 1/CNRS-INSU, Institut de Planetologie et d\'Astrophysique de Grenoble, Grenoble, France)
Lefloch, Beltrand (UJF-Grenoble 1/CNRS-INSU, Institut de Planetologie et d\'Astrophysique de Grenoble, Grenoble, France)

Abstract:
We present high spatial resolution (750 AU at 250 pc) maps of the B1 shock in the blue lobe of the L1157 outflow in four molecular lines at 2mm. The combined analysis of the morphology and spectral profiles has shown that the gas flowing at higher velocity (from 6 to 20 km/s with respect the systemic velocity of 2.6 km/s) is confined in a few compact (~ 5) clumps while the gas flowing at lower velocity traces the wall of the gas cavity excavated by the jet and the apex of the bow shock. These results confirm the complexity, both in the morphology and in the chemistry, of the B1 region, likely induced by the shock originated by the interaction between the driving precessing jet and the ambient material. A large velocity gradient model applied to the CS (3-2) and (2-1) lines provides the gas density of the compact high velocity (HV) clumps in the range of 5x10^3 ≤n(H2)≤ 5x10^5 cm^3, indicating that the clumps tend to be less dense than the large scale emitting gas. The origin of the clumps is still uncertain: the observed clumpiness could be the result of local instabilities produced by the interaction of the driving jet and the ambient medium or the HV clumps could be already present in the ambient medium before the advent of the outflow and they are excited and pushed by the arrival of the expanding outflow cavity.

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