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: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=690149
• 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）是银河系恒星之间的气体和尘埃，是一个巨大的储库，新的恒星和行星从中诞生，因此是理解星系演化的核心。气相从冷到热、分子到原子、中性到电离、动态重要的磁场和湍流运动，ISM 处于混乱之中。物理过程和天文现象的复杂性提高了我们理解团队中年轻研究人员的刺激性培训环境的能力，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。******使用普朗克卫星，我们在分析偏振热发射方面取得了巨大进展。 灰尘和相关磁场在天空上的投影中可见，缺乏深度理解所需的距离和 3D 视角。 然而，这种情况即将改变，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）可以在远处定位尘埃。 为了确保深入探测致密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，这是新型多路复用红外光谱仪 WIFIS 的一项新颖应用。为了获得最佳的角分辨率和 3D 分布，我们将使用赫歇尔基于热发射生成新的尘埃光学深度图。******尘埃如何随 3D 环境演化需要新的见解。 我们将重点关注一组独特的观测，这些观测在多个频率下明确测量相同的灰尘，旨在建立自洽的灰尘模型。亚毫米光学深度与光学消光的比率将被校准，量化 3D 不透明度的演变。 与热发射相比，利用蜻蜓长焦阵列卓越的宽视场灵敏度来测量散射光量，将通过反照率和相位函数提供补充证据。 与星际极化相比，热尘埃发射的分数极化的频率依赖性的 BLAST-TNG 观测将严格限制尘埃成分的混合物。******我们正在开发更复杂的 3D 模型和磁化 ISM 的静态和动态模拟，结合结构如何相对于磁场演化。 我们已经证明，在投影中，ISM 结构和磁场的相对方向在扩散介质中是平行的，但在高柱密度下是垂直的。我们将使用 BLAST-TNG 以更高的角分辨率进一步探索尘埃偏振。 我们的模型雄心勃勃地解决银河尘埃前景 B 模式偏振如何污染原始宇宙 B 模式信号、密集区域中的颗粒排列以及磁场在云聚集和支持中的作用。