On the velocity structure in clumpy planetary nebulae Café de grano o soluble: Micro-estructuras en...
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Transcript of On the velocity structure in clumpy planetary nebulae Café de grano o soluble: Micro-estructuras en...
On the velocity structure in clumpy planetary nebulae
Café de grano o soluble:Micro-estructuras en nebulosas planetarias
Wolfgang SteffenAlberto López
Instituto de AstronomíaUNAM, Ensenada
MyPN 5
Observations:
• Velocities of clumps up to > 500 km/s
• Linear velocity gradients for clumps and jets at large distances from the CS
• High speed tails up to ~ 200 km/s
Theory:
• Magnetic “jets” (García-Segura 1999) & Stagnation knots (Steffen, W. 2001) show linear v-gradients
This paper:
• Quasi-spherical clump distribution from instabilities and clumpy AGB-remnant overrun by fast post AGB-wind
NGC 2440
Abell 30
Borkowski et al. 1995
Borkowski et al. 1995
Chu et al. 1997 (X-Ray)
Borkowski et al. 1995
Images and velocities of fast head-tail structures
Abell 78
Meaburn et al. 1998
Images and velocities of very fast symmetric FLIERs
MyCn18, O’Connor, Meaburn et al.
García-Segura et al. 1999
Steffen, W., et al. 2001
Stagnation knots
Steffen & López in prep.
Fast stellar wind in 1 / r^2 environment (AGB-wind)
Dynamical instabilities
conv. shocksThermal instabilities
shock before cooling
Clumps due to dynamical and thermal instabilities
Distance [units 1e15 cm]
Vel
ocity
[cm
/s]
Steffen & López, in prep.
Fast stellar wind and pre-existing clumps
log
num
ber
dens
ity
density distribution
Shock acceleration of clouds
Speed of cloud after shock
wind
ambient medium
Steffen & López, in prep.
Simplified equation of motion
Continuous wind acceleration of clouds
Terminal velocity not equal local wind velocity
vc = F ( vi, r, vco, ro ) Clump velocity
vc_inf = G ( vi, vco, ro )
For large times evolution becomes self-similar.
Velocity vs. distance evolution
for 2 different clump densities
Low density
High density
Velocity vs. distance for different densities of cloudsfor fixed time
self-similar (low density)
not self-similar (high density)
Velocity vs. distance scatter plotpre-existing clouds
distance [cells]
Vel
ocity
200 km/s
1000 km/s
high density
low density
colour is log density
Velocity vs. distance scatter plotpre-existing clouds
distance [cells]
Vel
ocity
[c
m/s
]
model
low densitytails (not modeled)
colour is log density
Velocity vs. Density scatter plot
log density [1/ccm]
Vel
ocity
200 km/s
1000 km/s
pre-existing clouds instability clouds
Velocity spikes from tails of dense clumps
Distance [units 1e15 cm]
Vel
ocity
[cm
/s]
MyPN 3
Conclusions:
• Velocity stratification with density
• Initial shocked clump velocity ~ 1/r
• Linear velocity gradient for large r
• Multi-valued velocities at small r and high densities
• Velocity structure from instability clumps & pre-existing clumps is very different
More velocity and density diagnostics needed
MyPN 5
MyPN 5
Preexisting clumps and due to thermal instabilities
Distance [units 1e15 cm]
Vel
ocity
[cm
/s]