The origin of the Galactic center diffuse X-ray emission (GCDX) is still under intense investigation. We have found a clear excess in a longitudinal GCDX profile over a stellar number density profile in the nuclear bulge region, suggesting a significant contribution of diffuse, interstellar hot plasma to the GCDX. We have estimated that contributions of an old stellar population to the GCDX are about 50 % and 20 % in the nuclear stellar disk and nuclear star cluster, respectively. Our near-infrared polarimetric observations show that the GCDX region is permeated by a large scale, toroidal magnetic field. Together with observed magnetic field strengths in nearly energy equipartition, the interstellar hot plasma could be confined by the toroidal magnetic field.
Extragalactic Magnetism with SOFIA (SALSA Legacy Program). VII. A Tomographic View of Far-infrared and Radio Polarimetric Observations through MHD Simulations of Galaxies
The X-ray polarization degree of the molecular clouds that surround Sgr A* is expected to be greatly lowered because the polarized reflection emission is mixed with the unpolarized thermal emission that pervades the Galactic center region. Hence, this will be a challenging observation for the upcoming Imaging X-ray Polarimeter Explorer (IXPE). We aim to determine the detectability of four molecular clouds (MC) of the Sgr A complex (MC2, Bridge B2, Bridge E, and G0.11-0.11) in a realistic IXPE pointing of the Sgr A field of view. We assess the Minimum Detectable Polarization (MDP) increase when…
The Central 300 pc of the Galaxy probed by infrared spectra of H$_3^+$ and CO: part I. Predominance of warm and diffuse gas and high H$_2$ ionization rate
本文用3.5- 4.0PDMATHABMN m的H-$_3^+$线和2.34PDMATHABMN m附近的CO线的红外吸收光谱研究了银河系中央分子带（CMZ）的分子气体。除了先前报告的光谱，这些线的8颗恒星位于30 pc的Sgr A $^\ast$，现在有光谱$\sim$ 30明亮的恒星位于140 pc以西120 pc的Sgr A $^\ast$。光谱显示在大多数视线上存在温暖的（$T\sim 200$ K）和弥漫的（$n < 100 $ cm $^{-3}$）气体，$N$（H $_3^+$）$\sim 3 \times 10^{15} $ cm $^{-2}$。代替我们以前的分析，其中只考虑来自碳原子的光电离的电子，我们已经开发了一个简单的模型计算，其中宇宙射线电离的H $_2$和H也考虑在内。结果表明：（1）CMZ的体积主要是暖扩散气体;稠密气体的体积填充因子必须远小于0.1，CMZ并不像以前认为的那样不透明。X射线发射的超热10 $^8 $ K等离子体，其中一些人认为占主导地位的CMZ，不存在于扩展区域。(2)宇宙射线电离率为$ζ\sim 2 \times 10^{-14} $的$^{-1}$，比银河系致密云和弥散云分别高出$\sim$ 1000和$\sim$ 100倍。如果均分定律成立，这意味着一个大约为$\sim$ 100 $μ$ G的弥漫磁场。
We present the first mid-IR detection of the linear polarization toward the star CygOB2-12, a luminous blue hypergiant that, with Av of ~10 mag of foreground extinction, is a benchmark in the study of the properties of dust in the diffuse interstellar medium. The 8-13 micrometer spectropolarimetry, obtained with the CanariCam multi-mode camera at the Gran Telescopio Canarias (GTC), shows clear trends with wavelength characteristic of silicate grains aligned in the interstellar magnetic field. The maximum polarization, detected with 7.8 statistical significance near 10.2 micrometers, is (1.24 +…
Polarimetric Imaging of Sgr A* in its Flaring State
银河系的超大质量黑洞，Sgr A *，大约每6小时产生一次红外辐射爆发，有时还伴随着能量更高的X射线。近红外光子是由非热同步加速器过程产生的，但我们仍然不完全了解这些耀斑的起源和原因，也不知道X射线是如何发射的。辐射红外线的幂律电子可以被部分冷却，因此分布可以是具有（"冷却中断"）跃迁频率的中断幂律。此外，发射区似乎相当紧凑，可能仅限于吸积盘的内边缘。在这种情况下，X射线爆发本身可能是由于这个群体中能量最高的粒子的同步加速过程。在本文中，我们研究了这一建议的几个关键特征，产生相对论正确的偏振图像的Sgr A * 的近红外和X射线耀斑发射，以确定（1）是否测量的近红外偏振分数是符合这种几何形状，（2）是否预测的X射线到近红外峰值通量证实了目前可用的多波长观测。我们还计算了X射线偏振分数和位置角（相对于近红外光子），预计在未来几年的测量。我们表明，而X射线的偏振分数和位置角是相似的同步辐射冷却发射的近红外组件，这些数量是可测量的不同时，X射线出现从散射介质。因此，很明显，X射线偏振测量学的发展将成为研究超大质量黑洞附近时空的一个重要的新工具。
Detailed Interstellar Polarimetric Properties of the Pipe Nebula at Core Scales
我们使用R波段CCD线性偏振仪收集了约12000背景场恒星在46个领域的看法对烟斗星云的整个黑暗的云的偏振特性进行调查。根据2MASS的存档数据，我们估计调查区域的总视觉反射率在0.6 < Av < 4.6的范围内。虽然观察到的偏振显示出一个有序的大尺度模式，偏振矢量几乎垂直对准云的长轴，在核心尺度上，人们看到的细节是每个核心的特征。虽然许多观测到的恒星呈现出对普通星际介质来说不寻常的偏振度，但我们的分析表明，构成烟斗星云弥漫部分的尘埃颗粒似乎与正常的银河系星际介质具有相同的性质。偏振角的二阶结构函数的估计表明，大部分的烟斗星云是磁占主导地位，湍流是次Alvenic。烟斗星云当然是一个有趣的区域，在那里可以研究低质量恒星形成的初始阶段的主要过程。
YSO search toward the boundary of the Central Molecular Zone with near-infrared polarimetry
我们使用1.4米红外巡天望远镜上的近红外偏振照相机SIRPOL对中心分子区边界进行了近红外偏振测量，测量范围为（-1.4度$\lesssim l \lesssim$ -0.3度和1.0度$\lesssim l \lesssim$ 2.9度，$|b|\lesssim$ 0.1度）。根据Stokes $Q/I-U/I$平面上的星际偏振估计，我们选取了112个本征偏振源。选定的光源比$K_S=14.5$等亮，并且具有偏振不确定性$δP<1\,%$。当使用斯皮策空间望远镜中红外数据档案中的测光时，这些独特的偏振源中的十个与年轻恒星天体的光谱能量分布很好地拟合。然而，许多来源的光谱能量分布是遭受严重星际消光的正常恒星;这些可能是乌云后面的恒星。由于独特的偏振源和年轻天体候选者的数量很少，我们无法判断它们是否在中央分子带之外衰落。文献中许多大质量的年轻天体候选者只有很小的内禀极化。这可能表明它们的质量为4-15 M $_{\rm sun}$，其固有极化预计很小。
This paper calls attention to the relevance of Raman scattering by atomic hydrogen to three optical and near/mid-infrared spectral features of HI clouds: extended red emission (ERE), diffuse interstellar bands (DIBs), and the unidentified infrared bands (UIBs). DIBs, ERE, and UIBs are observed predominantly at the edge of HI clouds, are manifestly related, and remain poorly understood. Their salient properties correspond to two major characteristics of HI Raman scattering: unusual line broadenings and a concentration of the Raman scattered ultraviolet continuum in the vicinity of hydrogen's op…
The Optical -- Mid-infrared Extinction Law of the l=165 Sightline in the Galactic Plane: Diversity of Extinction Law in the Diffuse Interstellar Medium
An In-Depth View of the Mid-Infrared Properties of Point Sources and the Diffuse ISM in the SMC Giant HII Region, N66
本文利用斯皮策空间望远镜的红外光谱仪研究了低金属丰度（~0.2太阳）的巨大HII区N66的中红外点源和弥漫星际介质（ISM）。我们研究了14个有针对性的红外点源，以及光谱的扩散ISM是代表的光解离区域（PDR）和HII区域。在点源光谱，我们光谱确认，最明亮的中红外点源是一个大规模的嵌入式年轻恒星的对象，我们检测到硅酸盐的发射与两个年轻的星团，我们观察到光谱特征的一个已知的B[e]超巨星，更常见的是与赫比格Be星。在漫ISM中，我们提供了额外的证据表明，非常小的颗粒人口被光破坏的硬辐射场。11.3 μ m PAH复合物发射在点源和ISM光谱中都表现出无法解释的质心偏移，应在更高的信噪比和分辨率下进行研究。与其他地区的研究不同，6.2微米和7.7微米波段的通量是解耦的;数据点覆盖了I6.2/I11.3比值的窄带内的I7.7/I11.3 PAH比值的大范围。此外，在PAH电离中存在扩散，在辐射场相对较软的密集PDR中更中性，但在扩散ISM/PDR中电离。相比之下，PAH的尺寸分布似乎是独立的本地电离状态。对于河外低金属丰度恒星形成区尚未解决的研究很重要，我们发现来自红外亮点源的发射仅占整个区域PAH发射的20-35%。这些结果与其他具有类似硬辐射场和强辐射场的恒星形成区域进行了比较。
We report the SOFIA/HAWC+ band D (154$\,μ$m) and E (214$\,μ$m) polarimetric observations of the filamentary structure OMC-3 that is part of the Orion molecular cloud. The polarization pattern is uniform for both bands and parallel to the filament structure. The polarization degree decreases toward regions with high intensity for both bands, revealing a so called "polarization hole." We identified an optical depth effect in which polarized emission and extinction act as counteracting mechanisms as a potential contributor to this phenomenon. Assuming that the detected polarization is caused by t…
We searched for diffuse interstellar bands (DIBs) in the 0.91$<λ<$1.33 $μ$m region by analyzing the near-infrared (NIR) high-resolution ($R=20,000$ and 28,000) spectra of 31 reddened early-type stars ($0.04<E(B-V)<4.58$) and an unreddened reference star. The spectra were collected using the WINERED spectrograph, which was mounted on the 1.3 m Araki telescope at Koyama Astronomical Observatory, Japan, in 2012--2016, and on the 3.58 m New Technology Telescope at La Silla Observatory, Chile, in 2017--2018. We detected 54 DIBs -- 25 of which are newly detected by this study -- eight DIB candidates…
A first taste of MEAD (Measuring Extinction and Abundances of Dust) -- I. Diffuse Milky Way interstellar dust extinction features in JWST infrared spectra
We use spectral energy distribution (SED) fitting to place constraints on the stellar population properties of 29 quiescent ultra-diffuse galaxies (UDGs) across different environments. We use the fully Bayesian routine PROSPECTOR coupled with archival data in the optical, near, and mid-infrared from Spitzer and WISE under the assumption of an exponentially declining star formation history. We recover the stellar mass, age, metallicity, dust content, star formation time scales and photometric redshifts (photo-zs) of the UDGs studied. Using the mid-infrared data, we probe the existence of dust i…
