Grain Alignment and Polarization in Molecular Clouds

Wednesday, December 16, 2020 - 9:00am PST
Le Ngoc Tram
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Observations of polarized thermal dust emission toward molecular clouds hosted by an intense radiation source (i.e., massive stars) usually report a trend in which the fractional polarization p(%) first increases and decreases as the grain temperature Td increases. The latter trend differs from the prediction of the popular RAdiative Torques (RATs) alignment theory, which implies a monotonic increase of p(%) with Td. Moreover, polarimetric observations toward starless cores and protostars show the decrease of the p(%) with the visual extinction AV, which is known as “polarization hole”. We performed theoretical calculations of the degree of dust polarization by simultaneously considering the dust grain alignment and rotational disruption by RATs. Our theoretical prediction could successfully explain the observational p(%)-Td correlation in molecular clouds and the polarization hole toward starless cores and protostars.

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