‘Distance mapping’ and the 3D structure of BD +30° 3639

Authors

  • S. Akras,

    Corresponding author
    1. Instituto de Astronomía, Universidad Nacional Autónoma de México, Ensenada, Baja California, CP 22860, Mexico
      E-mail: akras@astrosen.unam.mx
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  • W. Steffen

    1. Instituto de Astronomía, Universidad Nacional Autónoma de México, Ensenada, Baja California, CP 22860, Mexico
    2. Institut für Computergraphik, Technische Universität Braunschweig, Braunschweig, 38106, Germany
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E-mail: akras@astrosen.unam.mx

ABSTRACT

BD +30° 3639 is a member of a group of uncommon planetary nebulae with Wolf–Rayet central star and higher expansion velocities in [O iii] than in [N ii] lines. Images and high-resolution spectra from the literature are used in order to construct a 3D model of the nebula using the morpho-kinematic code shape. We find that two homologous expansion laws are needed for the [N ii] and [O iii] shells. We conclude that the internal velocity field of BD +30° 3639 decreases with the distance from the central star at least between the [O iii] and [N ii] shells. A cylindrical velocity component is used to replicate the high-speed bipolar collimated outflows. We also present a new kinematic analysis technique called ‘distance mapping’. It uses the observed proper motion vectors and the 3D velocity field to generate maps that can be used as a constraint to the morpho-kinematic modelling with shape as well as improve the accuracy for distance determination. It is applied to BD +30° 3639 using 178 internal proper motion vectors from Li, Harrington & Borkowski and our 3D velocity field to determine a distance of 1.52 ± 0.21 kpc. Finally, we find evidence for an interaction between the eastern part of the nebula and the ambient H2 molecular gas.

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