Signatures of Magnetic Field Structure in Planetary Nebulae

Signatures of Magnetic Field Structure in

Planetary Nebulae

Signatures of Magnetic Field Structure in

Planetary Nebulae

P. J. Huggins, New York University

PNe as MHD systemsPNe as MHD systems

Can we see MHD in PNe ?

ample evidence for mag fields in PNe: jet origin – binary disks/single stars fields in AGB envelopes and proto/young-PNe surface fields CS PNe (Jordan et al. 05)

can we identify direct effects of MHD in PN images is the complex structure in PNe caused by MFs ? can structure be used to probe MF ?

we divide the question into 3 parts:

what to look for ? is there morphological evidence in PN images ? are the fields strong enough ?

Morphology of magnetic fields

1.4 GHz Lang et al. 99

171 Angstrom TRACE strong field cases: longitudinal coherencestrong field cases: longitudinal coherence

Molecular Clouds

gravity thermal pressureturbulencemagnetic field

right:filaments in Orion850 emission polarized Johnstone & Bally 99

left: elephant trunks in Rosette NebulaHCarlqvist et al. 03

Looking for MHD in PNe morphological signature: connectedness – filaments

PNe are different from the molecular cloud case: turbulence weak, radial velocity helps preserve geometry source of magnetic fields: central star 10” at 500 pc ~ 1017 cm, B~rn, n= 1,2,3 – uncertain

strategy search for connected structures examine what fields are needed to provide coherence

we present 3 exampleswe present 3 examples

NGC 3132

87” x 61”

tangential, multi-stranded, looped width ~ 4 1015 cm, l/w >60 proposal: magnetic filaments n ~ 105 cm-3, P ~ 10-9 dyne cm-2

NGC 3132 [O III] [N II] 12” x 19”

tangential, l/w>40, like spaghetti proposal: magnetic filaments n~4 104 cm-3, P~10-7 dyne cm-2

IC 418 H un-sharp mask 18” x 18”

tangential, l/w>40, like spaghetti proposal: magnetic filaments n~4 104 cm-3, P~10-7 dyne cm-2

IC 418 [N II], H un-sharp mask 18” x 18”

NGC 6537H, [N II]

field 9” x 8”

filaments part of torus n~104 cm-3, P~3 10-8 dynes

If filaments are magnetic are the fields strong enough ?

rough field estimates: = 8 P/B2 ~ 1, pressure = B2/4v2 ~ 1, n vexp

compare with AGB fields our estimates are upper limits 1/10 still robust likely compression

AGB – PN transition

“magnetic filament” concept consistent with AGB fields

~ mG at 1017 cm

Summary & Conclusions

Magnetic fields produce connected structures – filaments

PNe described here exhibit extreme filaments large length/width ratios & tangential, curved geometry field estimates consistent with fields in AGB envelopes

Proposal: filaments are signatures of magnetic field difficult to produce in any other way

Conclude: PN fields are localized and stringy Not convinced? Challenge: form similar filaments without fieldsNot convinced? Challenge: form similar filaments without fields