Poster Presentation
Tracing Dust Grain Properties in a Class 0 Envelope with Multi-wavelength ALMA Polarization
Presenter: Bich-Ngoc Nguyen (ASIAA/VNSC)
Understanding when and where dust grains begin to grow is a key question for constraining the initial conditions of planet formation. Protostellar envelopes and outflow cavities in Class 0 systems provide important environments for investigating this early dust evolution. We present preliminary results from a multi-wavelength ALMA polarization study of the isolated Class 0 protostar B335, using observations spanning 0.89--3.31 mm.
The polarization orientations are broadly consistent across the four wavelengths, indicating that the polarized emission traces a coherent magnetic-field morphology. In contrast, the polarization fraction increases toward longer wavelengths. In addition, the envelope exhibits lower values of the dust opacity spectral index, β<1, than the cavity-wall regions, which may indicate larger dust grains in the envelope. We also find that β is anticorrelated with the polarization fraction, with the strongest trend in Band 7. Regions with lower β tend to exhibit higher polarization fractions, consistent with larger and/or more efficiently aligned dust grains.
By combining multi-wavelength polarization measurements with SED-based estimates of β, our results suggest that the envelope of B335 may contain dust grains that have already evolved beyond typical interstellar grains. These findings point to possible early dust growth during the Class 0 phase. We will also discuss possible mechanisms that could explain the presence of large grains in the envelope.
asiaa.sinica.edu.tw