Squaring the circle: making sense of the dusty, magnetized interstellar medium beyond two dimensions

化圆为方：理解二维之外的尘埃磁化星际介质

• 批准号: RGPIN-2018-05965
• 负责人: Martin, Peter
• 金额: $ 3.64万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=713969
• 关键词: Squaring; circle; making; sense; dusty

The interstellar medium (ISM), gas and dust between the stars in the Milky Way, is a vast reservoir from which new stars and planets are being born, and so at the heart of understanding galaxy evolution. With gas phases ranging from cold to hot, molecular to atomic, and neutral to ionized, a dynamically important magnetic field, and turbulent motions, the ISM is in turmoil. The complexity of physical processes and astronomical phenomena stretch our ability to comprehend a stimulating training environment for young researchers on my team, who draw on computational astrophysics, statistics, and data-intensive analysis to apply a broad range of modern physics in very extreme conditions. Using the Planck satellite, we made great progress analysing polarized thermal emission. Dust and associated magnetic fields are seen in projection on the sky, lacking distances and the 3D perspective needed for deep understanding. However, this is about to change, a revolution launched by billions of stellar distances provided by the Gaia satellite. Quantifying dust extinction (scattering plus absorption) of stars locates the dust in distance. To ensure that dust in dense molecular star-forming clouds is probed deeply, my team will make spectral classifications of stars, a novel application of a new multiplexing infrared spectrograph WIFIS. For the best angular resolution, and so 3D distribution, we will produce new maps of dust optical depth based on thermal emission using Herschel. How dust evolves with 3D environment requires new insights. We will focus on a unique set of observations that explicitly measure the same dust at multiple frequencies, aiming for self-consistent dust models. The ratio of optical depth in the submillimetre to extinction in the optical will be calibrated, quantifying the evolution of opacity in 3D. Measuring the amount of scattered light, exploiting the superb wide field sensitivity of the Dragonfly Telephoto Array, compared to thermal emission will provide complementary evidence via albedo and phase function. BLAST-TNG observations of the frequency dependence of the fractional polarization of thermal dust emission compared to interstellar polarization will tightly constrain mixtures of dust components. We are developing more sophisticated 3D models and simulations of the magnetized ISM, both static and dynamic, incorporating how structures evolve in relation to the magnetic field. We have shown that in projection the relative orientation of ISM structures and the magnetic field is parallel in the diffuse medium, but perpendicular at high column density. We will explore dust polarization further with BLAST-TNG at higher angular resolution. Our models ambitiously tackle how the Galactic dust foreground B-mode polarization contaminates the primordial cosmological B-mode signal, grain alignment in dense regions, and the role of the magnetic field in cloud assembly and support.

星际介质(ISM)是银河系中恒星之间的气体和尘埃，是一个巨大的蓄水池，新的恒星和行星正在从中诞生，因此是理解星系演化的核心。由于气相从冷到热，从分子到原子，从中性到电离，这是一个动态重要的磁场，以及湍流运动，ISM处于混乱之中。物理过程和天文现象的复杂性使我们无法理解我们团队中年轻研究人员的激励培训环境，他们利用计算天体物理学、统计学和数据密集型分析在非常极端的条件下应用广泛的现代物理学。 利用普朗克卫星，我们在分析极化热发射方面取得了很大进展。在天空的投影中可以看到尘埃和相关的磁场，缺乏深入理解所需的距离和3D透视。然而，这种情况即将改变，这是一场由盖亚卫星提供的数十亿恒星距离发起的革命。量化恒星的尘埃消光(散射加吸收)可以定位距离上的尘埃。为了确保深入探测密集分子恒星形成云中的尘埃，我的团队将对恒星进行光谱分类，这是一种新的多路复用红外光谱仪WIFIS的新应用。为了获得最佳的角度分辨率，也就是3D分布，我们将使用Herschel制作基于热发射的新的尘埃光学厚度图。 尘埃如何在3D环境中演化需要新的见解。我们将重点放在一组独特的观测上，这些观测明确地在多个频率上测量相同的尘埃，旨在建立自洽的尘埃模型。将校准以亚毫米为单位的光学厚度与光学系统中的消光的比率，从而量化3D中不透明度的演变。测量散射光的数量，利用蜻蜓远摄阵列超强的广域灵敏度，与热发射相比，将通过反照率和相函数提供补充证据。BLAST-TNG观测到的热尘埃排放的偏振分数相对于星际偏振的频率依赖关系将严格限制尘埃成分的混合物。 我们正在开发更复杂的静态和动态磁化ISM的3D模型和模拟，包括结构如何随磁场演变。结果表明，在漫射介质中，ISM结构与磁场的相对取向是平行的，而在高柱密度下是垂直的。我们将利用BLAST-TNG在更高的角分辨率下进一步探索尘埃极化。我们的模型雄心勃勃地研究了银河系尘埃前景的B模偏振如何污染原始宇宙B模信号，密集区域的颗粒排列，以及磁场在云组装和支持中的作用。