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The CHESS spectral survey of star forming regions: Peering into the protostellar shock L1157-B1. II. Shock dynamics [Letter]

Lefloch, B., Cabrit, S., Codella, C., Melnick, G., Cernicharo, J., Caux, E., Benedettini, M., Boogert, A., Caselli, P., Ceccarelli, C., Gueth, F., Hily-Blant, P., Lorenzani, A., Neufeld, D., Nisini, B., Pacheco, S., Pagani, L., Pardo, J. R., Parise, Berengere, Salez, M., Schuster, K., Viti, S., Bacmann, A., Baudry, A., Bell, T., Bergin, E. A., Blake, G., Bottinelli, S., Castets, A., Comito, C., Coutens, A., Crimier, N., Dominik, C., Demyk, K., Encrenaz, P., Falgarone, E., Fuente, A., Gerin, M., Goldsmith, P., Helmich, F., Hennebelle, P., Henning, T., Herbst, E., Jacq, T., Kahane, C., Kama, M., Klotz, A., Langer, W., Lis, D., Lord, S., Maret, S., Pearson, J., Phillips, T., Saraceno, P., Schilke, P., Tielens, X., van der Tak, F., van der Wiel, M., Vastel, C., Wakelam, V., Walters, A., Wyrowski, F., Yorke, H., Bachiller, R., Borys, C., De lange, G., Delorme, Y., Kramer, C., Larsson, B., Lai, R., Maiwald, F. W., Martin-Pintado, J., Mehdi, I., Ossenkopf, V., Siegel, P., Stutzki, J. and Wunsch, J. H. 2010. The CHESS spectral survey of star forming regions: Peering into the protostellar shock L1157-B1. II. Shock dynamics [Letter]. Astronomy and Astrophysics 518 , L113. 10.1051/0004-6361/201014630

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Abstract

Context. The outflow driven by the low-mass class 0 protostar L1157 is the prototype of the so-called chemically active outflows. The bright bowshock B1 in the southern outflow lobe is a privileged testbed of magneto-hydrodynamical (MHD) shock models, for which dynamical and chemical processes are strongly interdependent. Aims. We present the first results of the unbiased spectral survey of the L1157-B1 bowshock, obtained in the framework of the key program “Chemical HErschel Surveys of star forming regions” (CHESS). The main aim is to trace the warm and chemically enriched gas and to infer the excitation conditions in the shock region. Methods. The CO 5-4 and o-H2O 110–101 lines have been detected at high-spectral resolution in the unbiased spectral survey of the HIFI-band 1b spectral window (555–636 GHz), presented by Codella et al. in this volume. Complementary ground-based observations in the submm window help establish the origin of the emission detected in the main-beam of HIFI and the physical conditions in the shock. Results. Both lines exhibit broad wings, which extend to velocities much higher than reported up to now. We find that the molecular emission arises from two regions with distinct physical conditions : an extended, warm (100 K), dense (3 × 105 cm-3) component at low-velocity, which dominates the water line flux in Band 1; a secondary component in a small region of B1 (a few arcsec) associated with high-velocity, hot (>400 K) gas of moderate density ((1.0–3.0) × 104 cm-3), which appears to dominate the flux of the water line at 179μm observed with PACS. The water abundance is enhanced by two orders of magnitude between the low- and the high-velocity component, from 8 × 10-7 up to 8 × 10-5. The properties of the high-velocity component agree well with the predictions of steady-state C-shock models.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: stars: formation; ISM: jets and outflows; ISM: individual objects: L1157
Additional Information: Special Issue: Herschel: the first science highlights. Pdf uploaded in accordance with publisher's policy at http://www.sherpa.ac.uk/romeo/issn/0004-6361/ (accessed 17/04/2014)
Publisher: EDP Sciences
ISSN: 0004-6361
Date of First Compliant Deposit: 30 March 2016
Last Modified: 27 May 2023 00:54
URI: https://orca.cardiff.ac.uk/id/eprint/52804

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