Polarization from Aligned Dust Grains in the β Pic Debris Disk
Authors
Dent, WRF
Publication Date
2022Journal Title
Astrophysical Journal
ISSN
0004-637X
Publisher
American Astronomical Society
Volume
930
Issue
1
Language
en
Type
Article
This Version
VoR
Metadata
Show full item recordCitation
Hull, C., Yang, H., Cortés, P., Dent, W., Kral, Q., Li, Z., Le Gouellec, V., et al. (2022). Polarization from Aligned Dust Grains in the β Pic Debris Disk. Astrophysical Journal, 930 (1) https://doi.org/10.3847/1538-4357/ac6023
Abstract
<jats:title>Abstract</jats:title>
<jats:p>We present 870 <jats:italic>μ</jats:italic>m Atacama Large Millimeter/submillimeter Array polarization observations of thermal dust emission from the iconic, edge-on debris disk <jats:italic>β</jats:italic> Pic. While the spatially resolved map does not exhibit detectable polarized dust emission, we detect polarization at the ∼3<jats:italic>σ</jats:italic> level when averaging the emission across the entire disk. The corresponding polarization fraction is <jats:italic>P</jats:italic>
<jats:sub>frac</jats:sub> = 0.51% ± 0.19%. The polarization position angle <jats:italic>χ</jats:italic> is aligned with the minor axis of the disk, as expected from models of dust grains aligned via radiative alignment torques (RAT) with respect to a toroidal magnetic field (<jats:italic>B</jats:italic>-RAT) or with respect to the anisotropy in the radiation field (<jats:italic>k</jats:italic>-RAT). When averaging the polarized emission across the outer versus inner thirds of the disk, we find that the polarization arises primarily from the SW third. We perform synthetic observations assuming grain alignment via both <jats:italic>k</jats:italic>-RAT and <jats:italic>B</jats:italic>-RAT. Both models produce polarization fractions close to our observed value when the emission is averaged across the entire disk. When we average the models in the inner versus outer thirds of the disk, we find that <jats:italic>k</jats:italic>-RAT is the likely mechanism producing the polarized emission in <jats:italic>β</jats:italic> Pic. A comparison of timescales relevant to grain alignment also yields the same conclusion. For dust grains with realistic aspect ratios (i.e., <jats:italic>s</jats:italic> > 1.1), our models imply low grain-alignment efficiencies.</jats:p>
Keywords
320, Interstellar Matter and the Local Universe
Sponsorship
National Science Foundation (NSF) (AST-1815784)
MEXT ∣ Japan Society for the Promotion of Science (JSPS) (18K13586, 20K14527)
National Aeronautics and Space Administration (NASA) (80NSSC18K1095)
Research Corporation for Science Advancement (RCSA) (Cottrell Scholar Award)
European Southern Observatory (ESO) (ESO Studentship)
Identifiers
apjac6023, ac6023, aas37249
External DOI: https://doi.org/10.3847/1538-4357/ac6023
This record's URL: https://www.repository.cam.ac.uk/handle/1810/336825
Rights
Licence:
http://creativecommons.org/licenses/by/4.0/
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