1998_09_Goetz_etal_10.1086_306058

1998_09_Goetz_etal_10.1086_306058 - THE ASTROPHYSICAL...

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T HE A STROPHYSICAL J OURNAL , 504:359 È 374, 1998 September 1 1998. The American Astronomical Society. All rights reserved. Printed in U.S.A. ( CEPHEUS A EAST: UNRAVELING THE MYSTERIES J ENNIFER A. J. L. W. J. D AN M. AND S. N. G OETZ ,P IPHER ,F ORREST ,W ATSON ,R AINES Department of Physics and Astronomy and C.E.K. Mees Observatory, University of Rochester, Rochester, NY 14627 C HARLES E. W OODWARD 1 Wyoming Infrared Observatory, Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071-3905 M. A. G REENHOUSE Goddard Space Flight Center, Greenbelt, MD 20771 H. A. S MITH Smithsonian Astrophysical Observatory, Cambridge, MA 02138 V. A. H UGHES Astronomy Group, Department of Physics, QueenÏs University at Kingston, Kingston, Ontario, Canada K7L 3N6 AND J. F ISCHER Naval Research Laboratory, Remote Sensing Division, Washington, DC 20375-5351 Received 1997 October 31; accepted 1998 April 7 ABSTRACT New infrared images of Cep A East are presented that show two regions of shock-excited line emission from separate bipolar Ñows. We identify the dominant sources powering the outÑows and argue that the results support a multiple outÑow model (Narayanan & Walker) as opposed to a quadrupolar outÑow scenario. The images include near-infrared broadband ( K [2.158 k m], L A [3.81 k m], and M @ [4.67 k m]) and spectral line ([Fe II ] emission line at 1.644 k m and 1 È 0 S [1] line at 2.122 k m) observations, as H 2 well as continuum emission, at 1.644 k m and 2.122 k m. Considering our data and other results, we present a uniÐed, self-consistent picture of the disk and shock structure. The northern emission region appears to be the result of the ablation of a dense molecular clump (coincident with HW 6) in the path of a diverting jet from YSO HW 2 and subsequent multiple bow shocks with prompt entrainment arising from the interaction of the jet with the molecular cloud Cep A-2. The southern line emission region near HW 7 resembles the ““ artillery shell ÏÏ bow shocks found in Orion and is most likely a J-type shock caused by a jet from another YSO, possibly HW 3(d)ii. Subject headings: H II regions È infrared: stars È ISM: individual (Cepheus A East) È ISM: molecules È stars: formation È stars: pre È main-sequence 1. INTRODUCTION We present here new near-infrared spectral imaging of the molecular cloud core Cepheus A East (hereafter Cep A East), a nearby site of massive star formation (Sargent 1977) located in the Cepheus OB association. Hiltner, & Blaauw, Johnson determined the distance to be 725 pc; the (1959) far-IR luminosity is 2.4 ] 10 4 which requires a cluster L _ , of B stars to excite. Cep A East harbors one of the Ðrst molecular bipolar outÑow sources discovered Ho, & Moran (RodriŁguez, Higher spatial resolution CO observations showed 1980). the outÑow to be extremely complex, and it was termed quadrupolar et al. & Walker (Torrelles 1993b). Narayanan present high spatial resolution J \ 3 ] 2 12 CO maps (1996) of the central 150 A that show the high-velocity (HV) red ( [ 4.5 to 9.6 km s ~1 ) and blue ( [ 26.9 to [ 12.8 km s ~1 ) lobes at a P.A. \ 80¡ È 90¡ close to the core and 102¡ at larger scales. The extra È high-velocity (EHV) red (10 to 60 km s ~1 ) and blue ( [ 60 to [
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1998_09_Goetz_etal_10.1086_306058 - THE ASTROPHYSICAL...

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