论文标题
$β$ PIC碎片磁盘中的对齐的灰尘颗粒的极化
Polarization from Aligned Dust Grains in the $β$ Pic Debris Disk
论文作者
论文摘要
我们提出了870 $μ$ M ALMA极化观测到来自标志性的，边缘碎片磁盘$β$ PIC的热粉尘发射。虽然空间分辨的映射未显示可检测到的极化灰尘发射，但当平均整个磁盘上的发射时，我们在$ \ sim $ 3 $σ$中检测到极化。相应的极化分数为$ p_ \ textrm {frac} $ = $ 0.51 \ pm 0.19 $％。偏光位置角度$χ$与磁盘的次要轴对齐，如通过辐射比对扭矩（大鼠）相对于环形磁场（$ b $ -rat）或相对于在辐射场（$ k $ rat）相对于环形磁场（$ b $ rat）的尘埃晶粒模型（大鼠）。当平均跨磁盘的外部和内部三分之二的极化发射时，我们发现极化主要来自SW第三。我们执行合成观测值，假设$ k $ -rat和$ b $ rat都可以通过谷物对齐。当在整个磁盘上平均发射时，两种模型都会产生接近我们观察到的值的极化部分。当我们平均磁盘的内部三分之二和外部三分之一的模型时，我们发现$ k $ -rat是在$β$ pic中产生偏振发射的可能机制。与谷物对齐相关的时间尺度的比较也得出相同的结论。对于具有逼真的长宽比（即$ s> 1.1 $）的尘埃晶粒，我们的模型意味着差异较低。
We present 870 $μ$m ALMA polarization observations of thermal dust emission from the iconic, edge-on debris disk $β$ Pic. While the spatially resolved map does not exhibit detectable polarized dust emission, we detect polarization at the $\sim$3$σ$ level when averaging the emission across the entire disk. The corresponding polarization fraction is $P_\textrm{frac}$ = $0.51 \pm 0.19$%. The polarization position angle $χ$ 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 ($B$-RAT) or with respect to the anisotropy in the radiation field ($k$-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 $k$-RAT and $B$-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 $k$-RAT is the likely mechanism producing the polarized emission in $β$ Pic. A comparison of timescales relevant to grain alignment also yields the same conclusion. For dust grains with realistic aspect ratios (i.e., $s > 1.1$), our models imply low grain-alignment efficiencies.
