Grain Alignment and Magnetic Field at the Galactic Centre from Polarized Dust Emission
Event date
-
Speaker
Akshaya Subbanna M S
Affiliation
KASI
Location
Online
Event Type
Teletalk

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I will discuss our recent study of the grain alignment physics at the Galactic Centre using the dust polarization data from SOFIA/HAWC+ and JCMT/SCUPOL at 53, 216, and 850 μm. We find that the observations here follow the predictions of RAdiative Torque (RAT) Alignment Theory except at long wavelength where we find evidence for the disruption of the grains as predicted by RAT Disruption mechanism. Magnetically Enhanced RAT alignment was found to play an important role in grain alignment due to the presence of a strong magnetic field (of the order of 5 mG) and can induce perfect alignment if the grains are superparamagnetic. A change in the ratio of polarization degree from p216μm/p850μm<1 to p216μm/p850μm>1 was observed indicating a change in the grain model from a composite to a separate population of carbon and silicate grains as predicted by previous numerical modeling. The grain alignment and disruption size for this regions was found to be around 0.1 μm and 1 μm respectively. The maximum polarization was observed from a region of low gas column density, high temperature, and order magnetic field and also corresponded to the region with the maximum size distribution of grains that could be aligned through MRAT mechanism.

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