IR AstronomyIR AstronomyIR AstronomyIR Astronomy

Planck Polarimetry and the Galactic Magnetic Field

Jennifer DelgadoTerry JonesTom JonesTheodore Wahl

IR AstronomyIR AstronomyIR AstronomyIR Astronomy

Planck will produce a 5’ resolution map of the fractional polarization and position angle of thermal dust emission for the entire galactic plane to ~ +/-5 degrees latitude!

IR AstronomyIR AstronomyIR AstronomyIR Astronomy

Dust grains aligned by the interstellar magnetic field produce polarization in transmission and emission.

IR AstronomyIR AstronomyIR AstronomyIR Astronomy

450 µm polarimetry with SPARO - H. Li et al. 2006

Imagine 5×105 pixels

IR AstronomyIR AstronomyIR AstronomyIR Astronomy

• The pitch of the local spiral arm.

• The location and characterization of major disturbances in the threaded (constant component) of the magnetic field (superbubbles).

• The overall geometry of the magnetic field throughout the entire disk, including major warps in the field.

• The global magnitude of the random component of the Galactic magnetic field and the large scale de-correlation length of this component.

• The power spectra of the fractional polarization and position angle for comparison with observations.

Large Scales

Intermediate Scales

IR AstronomyIR AstronomyIR AstronomyIR Astronomy

Polarization in Transmission increases with optical depth.Polarization in Emission decreases with optical depth.

Mean optical polarization.Fosalba et al. 2002

Far IR polarization.Jones 2004.

3/ 4P τ∝

1/ 4P τ −∝

IR AstronomyIR AstronomyIR AstronomyIR Astronomy

IR AstronomyIR AstronomyIR AstronomyIR Astronomy

Heiles compilation

Optical Stellar Polarization in Transmission

IR AstronomyIR AstronomyIR AstronomyIR Astronomy

Galactic Plane Infrared Polarization Survey (GPIPS)Clemens et al. 2007

NearIR Stellar Polarization

IR AstronomyIR AstronomyIR AstronomyIR Astronomy

Pavel, 2011

Comparison of Galactic Magnetic Field Models with Transmission Polarimetry Data

IR AstronomyIR AstronomyIR AstronomyIR Astronomy

Example, pure cylindrical geometry

Ted Wahl, unpublished

IR AstronomyIR AstronomyIR AstronomyIR Astronomy

Same latitude, different longitude

IR AstronomyIR AstronomyIR AstronomyIR Astronomy

Fosalba et al. 2002

Global Statistical Behavior

IR AstronomyIR AstronomyIR AstronomyIR Astronomy

NearIR - Jones, Klebe & Dickey 1992

IR AstronomyIR AstronomyIR AstronomyIR Astronomy

Giacalone & Jokipii 1999

How to model the random component?

Probably not this way:

IR AstronomyIR AstronomyIR AstronomyIR Astronomy

Code: TVD 3D 2nd order, ideal MHD code (Ryu & Jones 1995, Ryu et al. 1995, Ryu et al. 1998) updated to run in parallel on multiple cores.

Modeling Superbubble Formation

J.A. Delgado, P.J. Mendygral, T.J. Jones,T.W. Jones

Basic idea: Continuous injection of energy into a few central voxels to simulate multiple supernovae over 10`s of millions of years.

IR AstronomyIR AstronomyIR AstronomyIR Astronomy

15 Myr old superbubble (alone) as

seen in polarized thermal emission.

The bubble is 1.5 kpc away with no foreground or background.

Looking across field lines

IR AstronomyIR AstronomyIR AstronomyIR Astronomy

15 Myr old superbubble as seen in polarized thermal emission.

The bubble is 1.5 kpc away WITH foreground or background emission

from the galaxy.

Looking across field lines

IR AstronomyIR AstronomyIR AstronomyIR Astronomy

15 Myr old superbubble as seen

in transmission of starlight.

The bubble is 1.5 kpc away with a single ‘sheet’ of stars just behind the bubble.

Looking across field lines

IR AstronomyIR AstronomyIR AstronomyIR Astronomy

Conclusions

Planck Polarimetry will provide a spectacular data set for magnetic field studies in the diffuse ISM of the Milky Way.

Large scale structures and statistics can be analyzed using existing techniques and models.

Intermediate scale structures such as superbubbles,may be difficult to extract from polarimetry maps.