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Signatures of Magnetic Field Structure in Planetary Nebulae

P. J. Huggins, New York University. Signatures of Magnetic Field Structure in Planetary Nebulae. PNe 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

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Signatures of Magnetic Field Structure in Planetary Nebulae

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  1. P. J. Huggins, New York University Signatures of Magnetic Field Structure in Planetary Nebulae PNe as MHD systems

  2. 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 ?

  3. Morphology of magnetic fields 171 Angstrom TRACE 1.4 GHz Lang et al. 99 strong field cases: longitudinal coherence

  4. Molecular Clouds gravity thermal pressureturbulencemagnetic field • right:filaments in Orion850 memission polarized Johnstone & Bally 99 • left:elephant trunks in Rosette NebulaHaCarlqvist et al. 03

  5. 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 examples

  6. NGC 3132 87” x 61”

  7. 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”

  8. tangential, l/w>40, like spaghetti • proposal: magnetic filaments • n~4 104 cm-3, P~10-7 dyne cm-2 IC 418 Ha un-sharp mask 18” x 18”

  9. tangential, l/w>40, like spaghetti • proposal: magnetic filaments • n~4 104 cm-3, P~10-7 dyne cm-2 IC 418 [N II], Ha un-sharp mask 18” x 18”

  10. NGC 6537 Ha, [N II] field 9” x 8” • filaments part of torus • n~104 cm-3, P~3 10-8 dynes

  11. If filaments are magnetic are the fields strong enough ? • rough field estimates: • b = 8p P/B2 ~ 1, pressure • s = B2/4prv2 ~ 1, n vexp • compare with AGB fields • our estimates are upper limits • s ~ 1/10 still robust • likely compressionAGB – PN transition • “magnetic filament” concept consistent with AGB fields ~ mG at 1017 cm

  12. 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 fields

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