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Nature of shocks revealed by SOFIA OI observations in the Cepheus E protostellar outflow

Gusdorf, A. and Anderl, S. and Lefloch, B. and Leurini, S. and Wiesemeyer, H. and Güsten, R. and Benedettini, M. and Codella, C. and Godard, B. and Gómez-Ruiz, A. I. and Jacobs, K. and Kristensen, L. E. and Lesaffre, P. and des Forêts, G. Pineau and Lis, D. C. (2017) Nature of shocks revealed by SOFIA OI observations in the Cepheus E protostellar outflow. Astronomy and Astrophysics, 602 . Art. No. A8. ISSN 0004-6361.

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Context. Protostellar jets and outflows are key features of the star-formation process, and primary processes of the feedback of young stars on the interstellar medium. Understanding the underlying shocks is necessary to explain how jet and outflow systems are launched, and to quantify their chemical and energetic impacts on the surrounding medium. Aims. We performed a high-spectral resolution study of the [OI]_(63μm) emission in the outflow of the intermediate-mass Class 0 protostar Cep E-mm. The goal is to determine the structure of the outflow, to constrain the chemical conditions in the various components, and to understand the nature of the underlying shocks, thus probing the origin of the mass-loss phenomenon. Methods. We present observations of the O I ^3P_1 → ^3P_2, OH between ^2Π_(1/2)J = 3/2 and J = 1/2 at 1837.8 GHz, and CO (16–15) lines with the GREAT receiver onboard SOFIA towards three positions in the Cep E protostellar outflow: Cep E-mm (the driving protostar), Cep E-BI (in the southern lobe), and Cep E-BII (the terminal position in the southern lobe). Results. The CO (16–15) line is detected at all three positions. The [OI]_(63μm) line is detected in Cep E-BI and BII, whereas the OH line is not detected. In Cep E-BII, we identify three kinematical components in O I and CO. These were already detected in CO transitions and relate to spatial components: the jet, the HH377 terminal bow-shock, and the outflow cavity. We measure line temperature and line integrated intensity ratios for all components. The O I column density is higher in the outflow cavity than in the jet, which itself is higher than in the terminal shock. The terminal shock is the region where the abundance ratio of O I to CO is the lowest (about 0.2), whereas the jet component is atomic (N(O I)/N(CO) ~ 2.7). In the jet, we compare the [OI]_(63μm) observations with shock models that successfully fit the integrated intensity of 10 CO lines. We find that these models most likely do not fit the [OI]_(63μm) data. Conclusions. The high intensity of O I emission points towards the propagation of additional dissociative or alternative FUV-irradiated shocks, where the illumination comes from the shock itself. A picture emerges from the sample of low-to-high mass protostellar outflows, where similar observations have been performed, with the effects of illumination increasing with the mass of the protostar. These findings need confirmation with more observational constraints and a larger sample.

Item Type:Article
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URLURL TypeDescription Paper
Codella, C.0000-0003-1514-3074
Lis, D. C.0000-0002-0500-4700
Additional Information:© 2017 ESO. Article published by EDP Sciences. Received 18 January 2017; Accepted 31 March 2017; Published online 24 May 2017. This article uses Herschel-PACS data; Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. We thank an anonymous referee for meaningful comments that helped to improve the clarity and quality of this study. We thank the SOFIA operations and the GREAT instrument teams, whose support has been essential for the GREAT accomplishments, and the DSI telescope engineering team. Based [in part] on observations made with the NASA/DLR Stratospheric Observatory for Infrared Astronomy. SOFIA Science Mission Operations are conducted jointly by the Universities Space Research Association, Inc., under NASA contract NAS2-97001, and the Deutsches SOFIA Institut, under DLR contract 50 OK 0901. B. Lefloch acknowledges support from a grant from LabeX Osug2020 (Investissements d’avenir – ANR10LABX56). This work was supported by the French program “Physique et Chimie du Milieu Interstellaire” (PCMI) funded by the Centre National de la Recherche Scientifique (CNRS) and Centre National d’Études Spatiales (CNES).
Funding AgencyGrant Number
Deutsches SOFIA Institut (DSI)50 OK 0901
Agence Nationale pour la Recherche (ANR)ANR10LABX56
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Centre National d’Études Spatiales (CNES)UNSPECIFIED
Subject Keywords:astrochemistry – stars: formation – ISM: jets and outflows – ISM: individual objects: Cepheus E – ISM: kinematics and dynamics – infrared: ISM
Record Number:CaltechAUTHORS:20170928-141001804
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Official Citation:Nature of shocks revealed by SOFIA OI observations in the Cepheus E protostellar outflow A. Gusdorf, S. Anderl, B. Lefloch, S. Leurini, H. Wiesemeyer, R. Güsten, M. Benedettini, C. Codella, B. Godard, A. I. Gómez-Ruiz, K. Jacobs, L. E. Kristensen, P. Lesaffre, G. Pineau des Forêts and D. C. Lis A&A, 602 (2017) A8 DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:81905
Deposited By: Tony Diaz
Deposited On:28 Sep 2017 21:27
Last Modified:09 Mar 2020 13:18

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