A textbook case of bow shock entrainment in a YSO outflow |
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Authors: | Christopher J Davis Michael D Smith & Gerald H Moriarty-Schieven |
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Institution: | Joint Astronomy Centre, 660 North Aohoku Place, University Park, Hilo, Hawaii 96720, USA,;Dublin Institute for Advanced Studies, School of Cosmic Physics, 5 Merrion Square, Dublin 2, Ireland,;Astronomisches Institut, Universita¨t Wu¨rzburg, Am Hubland, D-97074 Wu¨rzburg, Germany |
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Abstract: | Near-infrared images in H2 line emission and submillimetre maps in CO J = 3–2 emission illustrate the remarkable association between a molecular bow shock and the redshifted molecular outflow lobe in W75N. The flow lobe fits perfectly into the wake of the bow, as one would expect if the lobe represented swept-up gas. Indeed, these observations strongly support the 'bow shock' entrainment scenario for molecular outflows driven by young stars. The characteristics of the bow shock and CO outflow lobe are compared with those of numerical simulations of jet-driven flows. These models successfully reproduce the bulge and limb-brightening in the CO outflow, although the model H2 bow exhibits more structure extending back along the flow axis. We also find that the size of the flow, the high mass fraction in the flow at low outflow velocities (low γ values) and the high CO/H2 luminosity ratio indicate that the system is evolved. We also predict a correlation, in evolved systems, between outflow age and the CO/H2 luminosity ratio. |
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Keywords: | circumstellar matter ISM: individual: W75N ISM: jets and outflows ISM: kinematics and dynamics infrared: ISM: lines and bands infrared: stars |
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