Astronomical imaging spectroscopy at far-infrared wavelengths

远红外波长的天文成像光谱

• 批准号: RGPIN-2016-06551
• 负责人: Naylor, David
• 金额: $ 7.07万
• 依托单位: University of Lethbridge
• 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=709253
• 关键词: Astronomical; imaging; spectroscopy; far; infrared

Approximately half of the radiant energy emitted by the universe falls in the far-infrared (FIR) spectral range (301000 µm) for two reasons: the first is that sources in the distant universe, galaxies in the local universe, or protostars in our own galaxy are often shrouded in dust and gas. The dust efficiently scatters and absorbs shorter wavelength radiation, which is subsequently re-radiated at longer wavelengths, both as continuum (dust) and line (ions, atoms, molecules) emission. The second reason is that distant galaxies do not decrease in IR brightness with increasing distance, because their emission is redshifted into the IR. Most of the FIR is inaccessible from the ground due to atmospheric absorption. Moreover, space borne instruments must operate at ~ 4 K to minimize their self-emission, which would otherwise dominate the weak astronomical signal. In previous FIR missions cooling was achieved by placing the entire telescope in a cryostat, limiting the diameters of primary mirrors to ~60 cm and resulting in relatively low spatial resolution. The Herschel Space Observatory broke this trend by employing a 3.5 m diameter passively cooled primary mirror located outside of the instrument payload, the instrument suite being cooled to ~4K. This design provided a major advance in spatial resolution and sensitivity, however, the latter remained limited by photon noise from the relatively warm (~80K) telescope. Potential gains in sensitivity of 2 -3 orders of magnitude exist by actively cooling large aperture telescopes as proposed for the ESA/JAXA SPICA mission. However, to realize these gains, the noise performance of the instruments themselves must be understood to a corresponding higher degree. This proposal has two components, the first is to continue to use data from Herschel/SPIRE in the study of the interstellar medium and the earliest stages of star formation, the time when molecular clouds fragment into cold and dense gravitationally bound cores. Starless cores can be probed by studying their thermal (continuum) emission, which provides information about the dust properties, and their line emission (or absorption), which provides information on the chemistry in these regions. Together they provide a unique window into the initial conditions of protostellar collapse. With its broad spectral coverage and intermediate resolution SPIRE is well suited to this task. The second component is to develop and evaluate the performance of a prototype of the spectrometer proposed for the SPICA/SAFARI instrument. A recently commissioned, large volume, low background, test facility cryostat will be used to study optical and thermal properties of key components of the spectrometer such as etalons, mechanisms and metrology. The ability to evaluate the performance of an integrated system at cryogenic temperatures will position Canada to be a partner of choice in future FIR space astronomy missions.

大约一半的宇宙辐射能量福尔斯在远红外（FIR）光谱范围（301000 µm），原因有二：第一是遥远宇宙中的辐射源，本地宇宙中的星系，或我们银河系中的原恒星通常被尘埃和气体所笼罩。尘埃有效地散射和吸收较短波长的辐射，随后以较长波长重新辐射，作为连续谱（尘埃）和线（离子，原子，分子）发射。第二个原因是，遥远星系的红外亮度不会随着距离的增加而降低，因为它们的辐射会红移到红外。 由于大气层的吸收，从地面无法进入大部分的飞行情报区。此外，星载仪器必须在~ 4K下工作，以尽量减少其自发射，否则自发射将主导微弱的天文信号。在以前的FIR任务中，冷却是通过将整个望远镜放置在低温恒温器中来实现的，将主镜的直径限制在60厘米左右，导致相对较低的空间分辨率。赫歇尔空间天文台打破了这一趋势，采用了一个直径为3.5米的被动冷却主镜，位于仪器有效载荷的外部，仪器套件被冷却到~4K。这种设计在空间分辨率和灵敏度方面取得了重大进展，然而，后者仍然受到相对温暖（~ 80 K）望远镜的光子噪声的限制。如为欧空局/日本宇宙航空研究开发机构SPICA使命提议的那样，通过主动冷却大孔径望远镜，灵敏度可能提高2 - 3个数量级。然而，为了实现这些增益，必须对仪器本身的噪声性能有更高的理解。 这个提议有两个组成部分，第一个是继续使用来自Herschel/SPIRE的数据来研究星际介质和星星形成的最早阶段，即分子云碎裂成寒冷而密集的引力束缚核心的时候。无星核可以通过研究它们的热（连续）发射来探测，这提供了关于尘埃特性的信息，以及它们的线发射（或吸收），这提供了这些区域的化学信息。它们一起提供了一个了解原恒星坍缩初始条件的独特窗口。凭借其广泛的光谱覆盖范围和中等分辨率，SPIRE非常适合这项任务。 第二个组成部分是开发和评价为SPICA/SAFARI仪器提议的光谱仪原型的性能。最近委托的一个大容量、低背景的测试设施低温恒温器将用于研究光谱仪关键部件的光学和热特性，如标准具、机械和计量。在低温下评价综合系统性能的能力将使加拿大成为未来远红外空间天文学飞行任务的首选伙伴。