2023/07/31 by Nguyen Chau Giang, Giang, Nguyen Chau, Thiem Hoang +1 · 1 citation
Biochemistry, Genetics and Molecular Biology · Physics and Astronomy · #Astro and Planetary Science #Astrophysics and Star Formation Studies #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Geomagnetism and Paleomagnetism Studies #Solar and Stellar Astrophysics (astro-ph.SR)
paper · pdf · doi:10.48550/arxiv.2307.16829
openalex publication_date 2023/07/31 · openalex created_date 2023/08/02 · openalex updated_date 2026/07/28
Thermal dust polarization is a powerful tool to probe magnetic fields (B) and grain properties. However, a systematic study of the dependence of dust polarization on grain properties in protostellar environments is not yet available. In this paper, we post-process a non-ideal MHD simulation of a collapsing protostellar core with our updated POLARIS code to study in detail the effects of iron inclusions and grain growth on thermal dust polarization. We found that superparamagnetic (SPM) grains can produce high polarization degree of p ∼ 10-40% beyond ∼ 500 au from the protostar because of their efficient alignment by magnetically enhanced Radiative Torque mechanism. The magnetic field tangling by turbulence in the envelope causes the decrease in p with increasing emission intensity I as p∝ Iα with the slope α∼ -0.3. But within 500 au, SPM grains tend to have inefficient internal alignment (IA) and be aligned with B by RATs only, producing lower p ∼ 1% and a steeper slope of α∼ -0.6. For paramagnetic (PM) grains, the alignment loss of grains above 1μm in the inner ∼ 200 au produces p << 1% and the polarization hole with α∼ -0.9. Grain growth can increase p in the envelope for SPM grains, but cause stronger depolarization for SPM grains in the inner ∼ 500 au and for PM grains in the entire protostellar core. Finally, we found the increase of polarization angle dispersion function S with iron inclusions and grain growth, implying the dependence of B-field strength measured using the DCF technique on grain alignment and grain properties.