Issue |
A&A
Volume 393, Number 3, October III 2002
|
|
---|---|---|
Page(s) | 1027 - 1033 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361:20020883 | |
Published online | 01 October 2002 |
The correlation between expansion velocity and morphology in planetary nebulae
Instituto de Astronomia y Meteorologia, Avenida Vallarta No. 2602, Col. Arcos Vallarta, C.P. 44130 Guadalajara, Jalisco, Mexico
Corresponding author: jpp@udgserv.cencar.udg.mx
Received:
19
March
2002
Accepted:
11
June
2002
It is usually accepted that the differing morphological classes of
planetary nebulae (PNe) arise from progenitors of differing mass. The
primary evidence for this derives from the differing galactic distributions
of the sources. This, if true, would be expected to result in other
differences as well, including variations in the kinematics of the nebular
envelopes.
We point out here that there is now sufficient evidence to determine that
this is the case. We find that BRET-type sources (i.e. nebulae
possessing “bipolar rotating episodic jets") have the lowest velocities of
expansion VEXP, followed (in order of increasing velocity) by bipolar
(BPNe), elliptical and circular nebulae. In addition to this, we find that the
distributions of circular, elliptical and bipolar sources are quite
distinct, with BPNe being biased towards lower velocities, and circular
sources distributed more uniformly. It appears therefore that bipolar
outflows contain, within the same shells, evidence for both the highest
and lowest velocities of expansion. Whilst the outer wings of these nebulae
are expanding at ~175 km s-1, the brighter parts of the shells (probably
corresponding to equatorial toroids) have velocities of only ~18 km s-1.
Key words: planetary nebulae: general / ISM: jets and outflows
© ESO, 2002
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