arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1909.09628astro-ph.SRastro-ph.EPastro-ph.GA
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用JVLA和ALMA解决由NGC1333 IRAS4A上的定向尘埃颗粒发射和消光引起的线偏振

Resolving Linear Polarization due to Emission and Extinction of Aligned Dust Grains on NGC1333 IRAS4A with JVLA and ALMA

Chia-Lin Ko, Hauyu Baobab Liu, Shih-Ping Lai, Tao-Chung Ching, Ramprasad Rao, Josep M. Girart

摘要:

本文报道了利用Karl G.在K(11.5-16.7 mm)、Ka(8.1-10.3 mm)和Q波段(6.3-7.9 mm)处使用Jansky超大阵列(JVLA),并且在波段6(1.2 mm)和波段7(0.85-0.89 mm)处使用Atacama大毫米阵列(ALMA)。在100-1000 AU的尺度上,所有这些观测都一致地跟踪了先前研究中所示的沙漏形磁场拓扑结构。在IRAS 4A 1最里面的100 AU区域中,在6.3-16.7 mm处检测到的偏振位置角(E场)是一致的,然而,与在1.2 mm和0.85-这样的90度偏移可以通过内部$\sim$ 100 AU区域在短于$\sim$ 1.5的波长处光学厚来解释毫米,从而观测探测对齐的尘埃对来自最里面区域的微弱或非偏振的温暖尘埃发射的吸收。这也可以解释为什么波段7的最高角分辨率ALMA图像显示,在IRAS 4A 1的内部$\sim$ 100 AU区域,偏振百分比随着尘埃亮度温度的增加而增加。根据这一解释,并假设尘埃颗粒与磁场对齐,根据IRAS 4A 1中心峰中旋转6.3-7.9 mm的90 $^{\circ}$推断的磁场位置角为$\sim-22^{\circ}$,这与流出方向$\sim-9^{\circ}$大致一致。

英文摘要:

We report high angular resolution observations of linearly polarized dust emission towards the Class 0 young stellar object (YSO) NGC1333 IRAS4A (hereafter, IRAS4A) using the Karl G. Jansky Very Large Array (JVLA) at K (11.5-16.7 mm), Ka (8.1-10.3 mm), and Q bands (6.3-7.9 mm), and using the Atacama Large Millimeter Array (ALMA) at Band 6 (1.2 mm) and Band 7 (0.85-0.89 mm). On 100-1000 AU scales, all of these observations consistently trace the hourglass shaped magnetic field topology as shown in the previous studies. In the innermost 100 AU region of IRAS4A1, the polarization position angles (E-field) detected at 6.3-16.7 mm are consistent, however, are nearly 90 degrees offset from those detected at 1.2 mm and 0.85-0.89 mm. Such a 90 degree offset may be explained by that the inner $\sim$100 AU area is optically thick at wavelengths shorter than $\sim$1.5 mm, whereby the observations probe the absorption of aligned dust against the weakly or unpolarized warm dust emission from the innermost region. This can also consistently explain why the highest angular resolution ALMA images at Band 7 show that the polarization percentage increases with dust brightness temperature in the inner $\sim$100 AU region of IRAS4A1. Following this interpretation and assuming that the dust grains are aligned with the magnetic fields, the inferred magnetic field position angle based on the 90$^{\circ}$ rotated at 6.3-7.9 mm in the central peak of IRAS4A1 is $\sim-22^{\circ}$, which is approximately consistent with the outflow direction $\sim-9^{\circ}$.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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