论文标题
极化功率光谱和尘埃云形态
Polarization power spectra and dust cloud morphology
论文作者
论文摘要
在CMB极化及其银河前景的研究框架中，热粉尘极化图的角度谱显示出了有趣的E/B不对称性和正相关性。在对这些观察结果的解释研究中，磁化的ISM尘埃云仅被视为丝状结构。但是，观察和理论证据也支持类似薄片的形状。在这项工作中，我们研究了云形状及其与局部磁场的连接对热灰尘图的角功率谱的影响。我们模拟了逼真的细丝和类似薄片的星际云，并使用软件$ Asterion $生成其热粉尘偏振的合成图。我们在[100,500] $中计算其在多极范围内的极化功率光谱$ \ ell \，并通过$ r_ {eb} $比率量化E/B功率不对称性，以及T和E模式之间的相关系数$ r^{te} $。我们量化$ r_ {eb} $和$ r^{te} $值在偏移角度（最长的云轴和磁场之间）以及嵌入常规或涡轮磁场中的两个云形状的倾斜角（在视线和磁场之间）的依赖性（在视线和磁场之间）。我们发现两个云形状都覆盖了（$ r_ {eb} $，$ r^{te} $）参数空间的相同区域。两种形状的倾斜度和偏移角度的依赖性相似，尽管类似板状结构通常显示出更大的散射。除了对偏移角度的已知依赖性之外，我们还发现倾斜角度的$ r_ {eb} $和$ r^{te} $的强依赖性。类似细丝和表格的结构可能导致具有相似（$ r_ {eb} $，$ r^{te} $）值的极化功率光谱的事实使它们的解释变得复杂。在将来的分析中，应考虑到与磁场几何形状的联系。
In the framework of studies of the CMB polarization and its Galactic foregrounds, the angular power spectra of thermal dust polarization maps have revealed an intriguing E/B asymmetry and a positive TE correlation. In interpretation studies of these observations, magnetized ISM dust clouds have been treated as filamentary structures only; however, sheet-like shapes are also supported by observational and theoretical evidence. In this work, we study the influence of cloud shape and its connection to the local magnetic field on angular power spectra of thermal dust polarization maps. We simulate realistic filament-like and sheet-like interstellar clouds, and generate synthetic maps of their thermal dust polarized emission using the software $Asterion$. We compute their polarization power spectra in multipole range $\ell \in [100,500]$ and quantify the E/B power asymmetry through the $R_{EB}$ ratio, and the correlation coefficient $r^{TE}$ between T and E modes. We quantify the dependence of $R_{EB}$ and $r^{TE}$ values on the offset angle (between longest cloud axis and magnetic field) and inclination angle (between line-of-sight and magnetic field) for both cloud shapes embedded either in a regular or a turbulent magnetic field. We find that both cloud shapes cover the same regions of the ($R_{EB}$, $r^{TE}$) parameter space. The dependence on inclination and offset angles are similar for both shapes although sheet-like structures generally show larger scatter. In addition to the known dependence on the offset angle, we find a strong dependence of $R_{EB}$ and $r^{TE}$ on the inclination angle. The fact that filament-like and sheet-like structures may lead to polarization power spectra with similar ($R_{EB}$, $r^{TE}$) values complicates their interpretation. In future analyses, this degeneracy should be accounted for as well as the connection to the magnetic field geometry.
