Please use this identifier to cite or link to this item:
|Title:||The structure of the Cepheus E protostellar outflow: The jet, the bowshock, and the cavity||Authors:||Lefloch, B.
Gómez-Ruiz, A. I.
|Issue Date:||2015||Journal:||ASTRONOMY & ASTROPHYSICS||Number:||581||First Page:||A4||Abstract:||Context. Protostellar outflows are a crucial ingredient of the star-formation process. However, the physical conditions in the warm outflowing gas are still poorly known. <BR /> Aims: We present a multi-transition, high spectral resolution CO study of the outflow of the intermediate-mass Class 0 protostar Cep E-mm. The goal is to determine the structure of the outflow and to constrain the physical conditions of the various components in order to understand the origin of the mass-loss phenomenon. <BR /> Methods: We have observed the J = 12-11, J = 13-12, and J = 16-15 CO lines at high spectral resolution with SOFIA/GREAT and the J = 5-4, J = 9-8, and J = 14-13 CO lines with HIFI/Herschel towards the position of the terminal bowshock HH377 in the southern outflow lobe. These observations were complemented with maps of CO transitions obtained with the IRAM 30 m telescope (J = 1-0, 2-1), the Plateau de Bure interferometer (J = 2-1), and the James Clerk Maxwell Telescope (J = 3-2, 4-3). <BR /> Results: We identify three main components in the protostellar outflow: the jet, the cavity, and the bowshock, with a typical size of 1.7″ × 21″, 4.5″, and 22″ × 10″, respectively. In the jet, the emission from the low-J CO lines is dominated by a gas layer at T<SUB>kin</SUB> = 80-100 K, column density N(CO) = 9 × 10<SUP>16</SUP> cm<SUP>-2</SUP>, and density n(H<SUB>2</SUB>) = (0.5-1) × 10<SUP>5</SUP> cm<SUP>-3</SUP>; the emission of the high-J CO lines arises from a warmer (T<SUB>kin</SUB> = 400-750 K), denser (n(H<SUB>2</SUB>) = (0.5-1) × 10<SUP>6</SUP> cm<SUP>-3</SUP>), lower column density (N(CO) = 1.5 × 10<SUP>16</SUP> cm<SUP>-2</SUP>) gas component. Similarly, in the outflow cavity, two components are detected: the emission of the low-J lines is dominated by a gas layer of column density N(CO) = 7 × 10<SUP>17</SUP> cm<SUP>-2</SUP> at T<SUB>kin</SUB> = 55-85 K and density in the range (1-8) × 10<SUP>5</SUP> cm<SUP>-3</SUP>; the emission of the high-J lines is dominated by a hot, denser gas layer with T<SUB>kin</SUB> = 500-1500K, n(H<SUB>2</SUB>) = (1-5) × 10<SUP>6</SUP> cm<SUP>-3</SUP>, and N(CO) = 6 × 10<SUP>16</SUP> cm<SUP>-2</SUP>. A temperature gradient as a function of the velocity is found in the high-excitation gas component. In the terminal bowshock HH377, we detect gas of moderate excitation, with a temperature in the range T<SUB>kin</SUB> ≈ 400-500 K, density n(H<SUB>2</SUB>) ≃ (1 -2) × 10<SUP>6</SUP> cm<SUP>-3</SUP> and column density N(CO) = 10<SUP>17</SUP> cm<SUP>-2</SUP>. The amounts of momentum carried away in the jet and in the entrained ambient medium are similar. Comparison with time-dependent shock models shows that the hot gas emission in the jet is well accounted for by a magnetized shock with an age of 220-740 yr propagating at 20-30 km s<SUP>-1</SUP> in a medium of density n(H<SUB>2</SUB>) = (0.5-1) × 10<SUP>5</SUP> cm<SUP>-3</SUP>, consistent with that of the bulk material. <BR /> Conclusions: The Cep E protostellar outflow appears to be a convincing case of jet bowshock driven outflow. Our observations trace the recent impact of the protostellar jet into the ambient cloud, produing a non-stationary magnetized shock, which drives the formation of an outflow cavity. <P />Appendices are available in electronic form at <A href="http://www.aanda.org/10.1051/0004-6361/201425521/olm">http://www.aanda.org||Acknowledgments:||We thank the referee Dr. Tim van Kempen and the Editor Malcolm Walmsley for detailed comments which have helped to improve the manuscript. We also 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 on observations made with the NASA/DLR Stratospheric Observatory for Infrared Astronomy, with the IRAM 30 m telescope and the IRAM Plateau de Bure Interferometer. 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. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). The James Clerk Maxwell Telescope is operated by the Joint Astronomy Centre on behalf of the Science and Technology Facilities Council of the United Kingdom, the Netherlands Organisation for Scientific Research, and the National Research Council of Canada. This work was partly supported by the CNRS program “Physique et Chimie du Milieu Interstellaire”, by the PRIN INAF 2012 – JEDI and by the Italian Ministero dell’Istruzione, Università e Ricerca through the grant Progetti Premiali 2012 – iALMA A.I. Gómez-Ruiz is supported by Consejo Nacional de Ciencia y Tecnología, through the program Cátedras CONACYT para Jóvenes Investigadores.||URI:||http://hdl.handle.net/20.500.12386/23758||URL:||https://www.aanda.org/articles/aa/abs/2015/09/aa25521-14/aa25521-14.html||ISSN:||0004-6361||DOI:||10.1051/0004-6361/201425521||Bibcode ADS:||2015A&A...581A...4L||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
Show full item record
Files in This Item:
|Lefloch_2015.pdf||PDF editoriale||2.98 MB||Adobe PDF||View/Open|
checked on Sep 29, 2020
checked on Sep 29, 2020
Items in DSpace are published in Open Access, unless otherwise indicated.