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]