The bow-shock and high-speed jet in the faint, 40 arcmin diameter, outer halo of the evolved Helix planetary nebula (NGC 7293)

被引:5
|
作者
Meaburn, J. [1 ]
Boumis, P. [2 ]
Akras, S. [2 ]
机构
[1] Univ Manchester, Jodrell Bank, Ctr Astrophys, Manchester M13 9PL, Lancs, England
[2] Natl Observ Athens, Inst Astron Astrophys Space Applicat & Remote Sen, GR-15236 Athens, Greece
关键词
ISM: jets and outflows; planetary nebulae: individual: Helix NGC 7293; CENTRAL STARS; PROPER MOTIONS; KNOTS; PARALLAXES; KINEMATICS; NGC-7293; OUTFLOWS;
D O I
10.1093/mnras/stt1580
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
In previous, very deep, optical images of NGC 7293, both a feature that has the morphology of a bow-shock and one with that of a jet, were discovered in the faint 40 arcmin diameter halo of the nebula. Spatially resolved longslit profiles of the H alpha and [N II] 6548, 6584 angstrom nebular emission lines from both features have now been obtained. The bow-shaped feature has been found to have H alpha radial velocities close to the systemic heliocentric radial velocity, -27 km s(-1), of NGC 7293 and is faint in the [N ii] 6548, 6584 A emission lines. Furthermore, the full width of these profiles matches the relative motion of NGC 7293 with its ambient interstellar medium consequently it is deduced that the feature is a real bow-shock caused by the motion of NGC 7293 as it ploughs through this medium. The proper motion of the central star also points towards this halo feature which substantiates this interpretation of its origin. Similarly [N ii] 6584 A line profiles reveal that the jet-like filament is indeed a collimated outflow, as suggested by its morphology, at around 300 km s(-1) with turbulent widths of around 50 km s(-1). Its low H alpha/[N ii] 6548, 6584 A brightness ratio suggests collisional ionization as expected in a high-speed jet.
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页码:3462 / 3468
页数:7
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