Probing Interstellar Grain Growth through Polarimetry in the Taurus Cloud Complex
Probing Interstellar Grain Growth through Polarimetry in the Taurus Cloud Complex
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DOI：
10.3847/1538-4357/abc6b0
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发表时间：
2020-10
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通讯作者：
J. Vaillancourt;B. Andersson;D. Clemens;V. Piirola;Thiem C. Hoang;E. Becklin;Miranda Caputo Lincoln Laboratory-Miranda-Capu
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作者：
J. Vaillancourt;B. Andersson;D. Clemens;V. Piirola;Thiem C. Hoang;E. Becklin;Miranda Caputo Lincoln Laboratory-Miranda-Capu
星光的光学和近红外(OIR)偏振通常被理解为星光被轴相对于局部磁场对准的尘埃颗粒对该光的二色性消光。取向颗粒布居的尺寸分布可以通过测量偏振的波长相关性来限制。产生对准的主要物理模型是辐射对准扭矩(RAT)，该模型预测最有效对准的颗粒是那些尺寸大于构成局部辐射场的光的波长的颗粒。因此，对于给定的颗粒尺寸分布，偏振达到最大值的波长()应该与尘埃颗粒和照明源之间视线上的特征变红相关。在此之前，已经建立了直到MAG的灭绝与变红之间的关联。我们将对这种关系的研究扩展到金牛座星云复合体中更大的恒星样本，包括消亡MAG。我们证实了MAG的早期结果，但发现MAG上的A-V关系是分叉的，部分样本延续了先前观察到的关系。剩下的样本表现出比A V更陡峭的上升。我们认为，显示急剧上升的数据代表了高密度“团块”的视线，那里发生了谷物凝结。我们提出了基于老鼠的模型来支持这些假设。这些结果表明，多波段OIR偏振测量是追踪分子云中颗粒生长的有力工具，与尘埃温度和发射率的不确定性无关。
The optical and near-infrared (OIR) polarization of starlight is typically understood to arise from the dichroic extinction of that light by dust grains whose axes are aligned with respect to a local magnetic field. The size distribution of the aligned-grain population can be constrained by measurements of the wavelength dependence of the polarization. The leading physical model for producing the alignment is that of radiative alignment torques (RATs), which predicts that the most efficiently aligned grains are those with sizes larger than the wavelengths of light composing the local radiation field. Therefore, for a given grain-size distribution, the wavelength at which the polarization reaches a maximum ( ) should correlate with the characteristic reddening along the line of sight between the dust grains and the illumination source. A correlation between and reddening has been previously established for extinctions up to mag. We extend the study of this relationship to a larger sample of stars in the Taurus cloud complex, including extinctions mag. We confirm the earlier results for mag but find that the versus A V relationship bifurcates above mag, with part of the sample continuing the previously observed relationship. The remaining sample exhibits a steeper rise in versus A V . We propose that the data exhibiting the steep rise represent lines of sight of high-density “clumps,” where grain coagulation has taken place. We present RAT-based modeling supporting these hypotheses. These results indicate that multiband OIR polarimetry is a powerful tool for tracing grain growth in molecular clouds, independent of uncertainties in the dust temperature and emissivity.