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Numerical simulations of wind-driven protoplanetary nebulae – I. near-infrared emission

Novikov, Igor D, Smith, Michael D. (2018) Numerical simulations of wind-driven protoplanetary nebulae – I. near-infrared emission. Monthly Notices of the Royal Astronomical Society, 480 (1). pp. 75-95. ISSN 0035-8711. (doi:10.1093/mnras/sty1842) (KAR id:68509)

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Abstract

To understand how the circumstellar environments of post-Active Giant Branch (AGB) stars develop into planetary nebulae, we initiate a systematic study of 2D axisymmetric hydrodynamic simulations of protoplanetary nebula (pPN) with a modified ZEUS code. The aim of this first work is to compare the structure of prolate ellipsoidal winds into a stationary ambient medium where both media can be either atomic or molecular. We specifically model the early twin-shock phase which generates a decelerating shell. A thick deformed and turbulent shell grows when an atomic wind expands into an atomic medium. In all other cases, the interaction shell region fragments into radial protrusions due to molecular cooling and chemistry. The resulting fingers eliminate any global slip parallel to the shell surface. This rough surface implies that weak shocks are prominent in the excitation of the gas despite the fast speed of advance. This may explain why low-excitation molecular hydrogen is found towards the front of elliptical pPN. We constrain molecular dissociative fractions and time-scales of fast H2 winds and the pPN lifetime with wind densities ∼105cm−3 and shock speeds of 80∼200kms−1⁠. We identify a variety of stages associated with thermal excitation of H2 near-infrared emission. Generated line emission maps and position–velocity diagrams enable a comparison and distinction with post-AGB survey results. The 1→0S(1)&2→1S(1) lines are lobe-dominated bows rather than bipolar shells.

Item Type: Article
DOI/Identification number: 10.1093/mnras/sty1842
Uncontrolled keywords: hydrodynamics, shock waves, ISM: jets and outflows, ISM: molecules
Subjects: Q Science
Divisions: Faculties > Sciences > School of Physical Sciences
Depositing User: Michael Smith
Date Deposited: 07 Aug 2018 11:18 UTC
Last Modified: 31 Oct 2019 10:52 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/68509 (The current URI for this page, for reference purposes)
Smith, Michael D.: https://orcid.org/0000-0002-4289-5952
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