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Magnetic fields in Planetary and Proto Planetary. Nebulae. Laurence Sabin (IAC ,SPAIN / Manchester,UK) ‏. A.A. Zijlstra (Manchester,UK) and J.S. Greaves (St Andrews,UK) ‏. 3 Shaping Models. ✸ Wind-Wind interaction . BUT need of initial axisymmetrical structure.

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slide1

Magnetic fields in Planetary and Proto Planetary

Nebulae

Laurence Sabin(IAC ,SPAIN / Manchester,UK)‏

A.A. Zijlstra (Manchester,UK) and J.S. Greaves (St Andrews,UK)‏

3 shaping models
3 Shaping Models
  • ✸Wind-Wind interaction. BUT need of initial axisymmetrical structure.
  • ✸Binarity. BUT lack of observational evidence.
  • ✸Magnetic fields (B): detectable, measurable (spectropolarimetry) , local (maser:H2O). AND Can a single star supply the energy necessary to create a strong Bfield ?
magnetic model
Magnetic Model

I) Detection of global magnetic fields.

II) Characteristics of the field in 4 bipolar objects

III) Relation with the physical properties of the targets.

IV) What is the role of B in the shaping of Post-AGBs and PNe?

observations
Observations
  • SCUBA at the JCMT
  • Bands: 450 µm and 850 µm ( jiggle-map mode)‏
  • Dust distribution and polarization.
  • Dust grains have their long axis B
  • No strength value
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The Sample

Small : 4 objects

Unique : NO other known data

“Death” of SCUBA

ngc 6537
NGC 6537

HST data

slide7

NGC 6537: HST vs SCUBA

  • Strong Bipolar PN

Hot central star (1.5-2.5 x 10^ 5 K)‏

  • O-rich
  • Submm size: ~ 20 x 20 arcsec²
ngc 6537 at 850 m b
NGC 6537 at 850µm: B

Magnetic Field distribution:

- Does not cover all the nebula

- Organized (1 main direction)‏

- Consistent (small variation of polarization degree & no change in geometry)‏

Bfield in the SE-NW direction = equatorial plane

Well defined toroidal magnetic field.

mp:(11.2 ± 2.2) %, ma: (26.5 ± 5.7) °

ngc 7027
NGC 7027

Credit: W. B. Latter et al., HST, NICMOS

ngc 7027 hst vs scuba
NGC 7027: HST vs SCUBA
  • Young Bipolar PN
  • C-rich

Submm size: ~ 40 x 36 arcsec²

ngc 7027 at 450 m b
NGC 7027 at 450 µm: B

B distribution :

  • -All over the nebula
  • -Mainly along the equatorial plane -Field disturbed in the SW.
  • -Lower degree of polarization in the center: no coherence of B (ionization)‏

Toroidal magnetic field.

NE: mp=8.9±0.9 % SW: mp=7.6±1.3 %

ngc 6302
NGC 6302

2,2m ESO.Courtesy: R. Corradi & A. Zijlstra

ngc 6302 2 2meso vs scuba
NGC 6302: 2.2mESO vs SCUBA

Bipolar PN

O-Rich

Submm size:

~ 1.7 x 1 arcmin²

ngc 6302 at 450 m
NGC 6302 at 450 µm

Bdistribution:

  • -Does not cover all the nebula
  • -Few polarization vectors
  • -B consistent & organized
  • -No alignment with the equatorial plane

mp: (11.4 ±1.6) % ma: (32.7± 4.6)°

ngc 6302 at 450 m1
NGC 6302 at 450 µm

B localized and aligned at the radio core position : Not Toroidal

crl 2688
CRL 2688

HST data. Credit: R. Sahai, J. Trauger

crl 2688 hst vs scuba
CRL 2688: HST vs SCUBA

PPN

C-rich

Binary?

Submm size: ~ 60 x 45 arcsec²

Composite: Visible+ IR

HST data. Credit: R. Sahai, J. Trauger, R. Thompson

crl 2688 at 850 m
CRL 2688 at 850 µm
  • Bdistribution:
  • - Covers the entire nebula
  • -Field locally broken
  • -Decrease of
  • polarization degree (torus interaction)‏
  • -Two main directions

POLOIDAL & TOROIDAL magnetic fields

mp: 1.4% - 3.2 % - 8.8%

crl 2688 at 450 m
CRL 2688 at 450 µm
  • Bdistribution: Same conclusion as for the 850µm data.
  • (higher resolution)‏
  • - Covers most of nebula
  • - Two main directions
  • - Undersampling
relation between b and the physical properties of the pne ppn
Relation between B and the physical properties of the PNe/PPN ?
  • 1-Chemistry :
  • C-rich (CRL 2688 & NGC 7027) : Disorganized B located all over the nebula
  • O-rich (NGC 6537 & NGC 6302): Organized B near the central region
  •  Dependence on the nature , geometry and size of the dust grains. Need of models.
relation between b and the physical properties of the pne ppn1
Relation between B and the physical properties of the PNe/PPN ?
  • 2- Evolutionary stage:
  • Nebulae extent : CRL 2688, NGC 7027, NGC 6537 and NGC 6302.
  • Younger Nebulae: Disorganized B
  • Older Nebulae: Organized B
  •  Long lived B.
  •  Toroidal magnetic fields are becoming dominant while the nebulae evolve. Need of observations.
scenario for pne ppn shaping with magnetic fields
Scenario for PNe/PPN shaping with magnetic fields
  • AGB star = dipole-like
  • Action of companion for toroidal B ****
  • Poloidal field carried by the outflows
  • Toroidal field getting more organized and magnetic field becomes more important/dominant.

AGB

PPN

PN

**** Re-seeding process (J. Nordhaus, APN4)

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More details:

Sabin L. , Zijlstra A.A, and Greaves J.S, 2007, MNRAS, Vol 376-378

Greaves J.S., 2002 , A&A, Vol 392, p L1-L4