Title: SOFIA Polarization Spectrum of Three Star-Forming Clouds Show Chinese title

Title: SOFIA 三条恒星形成云的偏振光谱

Abstract: The dust emission polarization spectrum -- how the polarization percentage changes with wavelength -- serves as a probe of dust grain properties in star-forming regions. In this paper, we present 89 $\mu$m - 214 $\mu$m polarization spectrum measurements obtained from SOFIA/HAWC+ for three star-forming clouds -- OMC1, M17, and W3. We find that all three clouds have an overall decreasing polarization percentage with increasing wavelength (i.e., a ``falling polarization spectrum''). We use SOFIA and Herschel data to create column density and temperature maps for each cloud. We fit for the slope of the polarization spectrum at each sky position in each cloud, and using the Pearson $r$ coefficient we probe each cloud for possible correlations of slope with column density and slope with temperature. We also create plots of slope vs. column density and slope vs. temperature for each cloud. For the case of OMC1, our results are consistent with those presented by J. Michail et al., who carried out a similar analysis for that cloud. Our plots of polarization spectrum slope vs. column density reveal that for each cloud there exists a critical column density below which a falling polarization spectrum is not observed. For these more diffuse sightlines, the polarization spectrum is instead flat or slightly rising. This finding is consistent with a hypothesis presented 25 years ago in a paper led by R. Hildebrand based on Kuiper Airborne Observatory data. This hypothesis is that regions shielded from near-IR radiation are required to produce a sharply falling polarization spectrum. Show Chinese abstract

Abstract: 尘埃发射偏振谱——偏振百分比随波长的变化——作为研究恒星形成区域尘埃颗粒特性的探针。 在本文中，我们展示了通过SOFIA/HAWC+获得的三个恒星形成云——OMC1、M17和W3——的89$\mu$m - 214$\mu$m偏振谱测量结果。 我们发现这三个云的偏振百分比随着波长的增加而整体下降（即“下降的偏振谱”）。 我们使用SOFIA和Herschel数据为每个云创建柱密度和温度图。 我们在每个云中的每个天空位置拟合偏振谱的斜率，并使用Pearson$r$系数来探测每个云中斜率与柱密度以及斜率与温度之间可能的相关性。 我们还为每个云创建了斜率与柱密度以及斜率与温度的图表。 对于OMC1的情况，我们的结果与J. Michail等人提出的结论一致，他们对该云进行了类似的分析。 我们绘制的偏振谱斜率与柱密度的图表显示，对于每个云来说，存在一个临界柱密度，低于该密度时不会观察到下降的偏振谱。 对于这些更稀疏的视线方向，偏振谱则是平坦的或略微上升的。 这一发现与25年前由R. Hildebrand领导的一篇论文中提出的一个假设一致，该论文基于Kuiper机载天文台的数据。 该假设是，要产生急剧下降的偏振谱，需要处于近红外辐射屏蔽的区域。