jennifer delgado terry jones tom jones theodore...
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IR AstronomyIR AstronomyIR AstronomyIR Astronomy
Planck Polarimetry and the Galactic Magnetic Field
Jennifer DelgadoTerry JonesTom JonesTheodore Wahl
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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!
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Dust grains aligned by the interstellar magnetic field produce polarization in transmission and emission.
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450 µm polarimetry with SPARO - H. Li et al. 2006
Imagine 5×105 pixels
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• 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
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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 −∝
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Heiles compilation
Optical Stellar Polarization in Transmission
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Galactic Plane Infrared Polarization Survey (GPIPS)Clemens et al. 2007
NearIR Stellar Polarization
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Pavel, 2011
Comparison of Galactic Magnetic Field Models with Transmission Polarimetry Data
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Example, pure cylindrical geometry
Ted Wahl, unpublished
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Same latitude, different longitude
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Fosalba et al. 2002
Global Statistical Behavior
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NearIR - Jones, Klebe & Dickey 1992
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Giacalone & Jokipii 1999
How to model the random component?
Probably not this way:
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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.
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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
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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
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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
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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.
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