Magnetic fields in Planetary and Proto Planetary Magnetic fields in Planetary and Proto Planetary

Laurence Sabin (IAC ,SPAIN / Manchester,UK)

Nebulae

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

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

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

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

The Sample

Small : 4 objects

Unique : NO other known data

“Death” of SCUBA

NGC 6537

HST data

NGC 6537: HST vs SCUBA

Submm size: ~ 20 x 20 arcsec² Strong Bipolar PN

Hot central star (1.5-2.5 x 10^ 5 K)

O-rich

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

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

NGC 7027: HST vs SCUBA

Submm size: ~ 40 x 36 arcsec² Young Bipolar PN

C-rich

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

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

NGC 6302: 2.2mESO vs SCUBA

Bipolar PN

O-Rich

Submm size:

~ 1.7 x 1 arcmin²

NGC 6302 at 450 µm

B distribution:

-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 µm

B localized and aligned at the radio core position : Not

Toroidal

CRL 2688

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

CRL 2688: HST vs SCUBA

Composite: Visible+ IR

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

R. Thompson

Submm size: ~ 60 x 45 arcsec²

PPN

C-rich

Binary?

CRL 2688 at 850 µm

B distribution:

- Covers the entire

nebula

-Field locally broken

-Decrease of

polarization degree

(torus interaction)

-Two main directions

POLOIDAL & TOROIDAL

magnetic fieldsmp: 1.4% - 3.2 % - 8.8%

CRL 2688 at 450 µm

B distribution: 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 ?

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/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

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)

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