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: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=658903
• 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），恒星之间的气体和灰尘以银河系为巨大的水库，新的恒星和行星正在诞生，因此是理解星系进化的核心。气相范围从冷到热，分子到原子，并且中性到电离，动态重要的磁场和湍流运动，ISM处于动荡状态。物理过程和天文现象的复杂性扩大了我们的理解能力 - 我团队中的年轻研究人员的刺激训练环境，他们利用计算机天体物理学，统计数据和数据密集型分析，在非常极端的条件下应用了广泛的现代物理。在天空的投影中可以看到灰尘和相关的磁场，缺乏距离和深层理解所需的3D透视图。但是，这将要改变，这是盖亚卫星提供的数十亿个恒星距离发起的革命。量化尘埃延伸（散射加滥用）的星星将灰尘置于距离。为了确保深入探测密集的分子恒星形成云的灰尘，我的团队将对恒星进行光谱分类，这是一种新的多重红外光谱仪WiFis的新颖应用。为了获得最佳的角度分辨率以及SO 3D分布，我们将基于使用Herschel的热发射来生成新的灰尘光学深度图。我们将专注于一组独特的观测值，这些观察值在多个频率下明确测量相同的灰尘，以实现自洽的灰尘模型。将校准亚亚毫米列中的光学深度与扩展的比率，从而量化3D不透明度的演变。与热发射相比，测量散落的光的量，利用蜻蜓远摄阵列的出色宽场灵敏度将通过反照率和相位功能提供完整的证据。与星际极化相比，热灰尘发射的分数极化的频率依赖性观察到了灰尘成分的紧密约束混合物。我们已经表明，在投影中，ISM结构的相对方向和磁场在漫射介质中平行，但在高柱密度下垂直。我们将在较高的角度分辨率下通过BLAST-TNG进一步探索灰尘极化。我们的模型雄心勃勃地解决了银河尘埃前景B模式极化如何污染原始宇宙学B模式信号，密集区域中的晶粒对准以及磁场在云组装和支撑中的作用。