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    National Tsing Hua University Institutional Repository > 理學院 > 天文研究所 > 會議論文  >  A pair of close YSOs with strikingly different outflow ejection geometry


    Please use this identifier to cite or link to this item: http://nthur.lib.nthu.edu.tw/dspace/handle/987654321/53744


    Title: A pair of close YSOs with strikingly different outflow ejection geometry
    Authors: Torrelles, José M.;Patel, Nimesh A.;Anglada, Guillem;Gómez, José F.;Ho, Paul T. P.;Lara, Lucas;Alberdi, Antonio;Cantó, Jorge;Curiel, Salvador;Garay, Guido;Rodríguez, Luis F
    教師: 賀曾樸
    Date: 2005
    Relation: Proceedings of the International Astronomical Union (2005), 1: 186-189
    Keywords: YSOs
    strikingly different outflow
    ejection geometry
    Abstract: We present Very Long Baseline Array (VLBA) proper motion observations of water masers toward two young stellar objects (YSOs) of the W75N(B) high-mass star forming region. These observations (Torrelles et al. 2003) show two objects having a similar spectral type (early-B stars), separated in the sky by 00^''7 (corresponding to 1400 AU at the source distance), sharing the same molecular gas environment, but presenting a strikingly different outflow ejection geometry. One of these YSOs, W75N(B)-VLA 1, has a jet-like outflow at 2000 AU scale, with the water masers moving at velocities of ≃20 km s^{-1} along the major axis of the thermal radio continuum jet, while the other YSO has a water maser shell outflow of 160 AU radius expanding at ≃30 km s^{-1} in multiple directions with respect to the central compact radio continuum source W75N(B)-VLA 2. Given the small dynamical time obtained for the water maser shell (≃13 yr), we propose that in the very early stages of the star-formation process there may exist short lived, possibly repetitive, events associated with very poorly collimated outflows. All these results suggest that outflow collimation is not only a consequence of ambient conditions, but something intrinsic to the evolution of the individual stars, opening the important question of how and when these non-collimated wind ejection events occur in the evolution of YSOs. Although we argue in this paper that W75N(B)-VLA 2 could be in an earlier stage of evolution than W75N(B)-VLA 1, we think that observations at (sub)millimeter wavelengths with angular resolutions of ≃0^''1 can provide the key for determining the relative stage of evolution of these two remarkable YSOs.
    URI: http://nthur.lib.nthu.edu.tw/dspace/handle/987654321/53744
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