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: 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=692590
• 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.********

宇宙发出的辐射能量的大约一半落在远红外（FIR）光谱范围（301000 µm）中，原因有两个：第一个是遥远的宇宙中的来源，当地宇宙中的星系或我们自己的星系中的代理恒星通常在灰尘和气体中笼罩。灰尘有效地散射并吸收较短的波长辐射，随后在更长的波长下重新辐射，无论是连续的（灰尘）和线（离子，原子，分子）发射。第二个原因是，远处星系不会随着距离的增加而在IR亮度中降低，因为它们的发射被红移到IR中。 ***由于大气滥用，大多数FIR在地面上都无法访问。此外，诞生的仪器必须以〜4 k的速度运行，以最大程度地减少其自我发射，否则将主导天文信号。在先前的FIR任务中，通过将整个望远镜放在低温恒温器中，将冷却量限制为〜60 cm，并导致相对低的空间分辨率。 Herschel空间天文台通过使用位于仪器有效载荷外部的直径为3.5 m的被动冷却的主镜子，打破了这一趋势，仪表套件被冷却至〜4K。这种设计为空间分辨率和灵敏度提供了重大进步，但是，后者仍然受到相对温暖（〜80K）望远镜的光子噪声的限制。通过为ESA/JAXA SPICA任务提出的积极冷却大量孔径望远镜，存在2-3个数量级的敏感性增长。但是，要意识到这些收益，必须将乐器本身的噪声性能理解为相应的更高程度。****该提案有两个组件，首先是在研究星际培养基的研究中继续使用来自赫尔谢尔/尖刺的数据，而恒星形成的最早阶段，是分子云碎片和密集的重力构造的时间。可以通过研究其热（连续性）发射来探测无星核，该发射提供有关灰尘特性及其线排放（或滥用）的信息，这些信息提供了有关这些地区化学性质的信息。它们共同提供了一个独特的窗口，进入了原始崩溃的初始条件。凭借其广泛的覆盖范围和中间分辨率的尖顶非常适合此任务。最近委托的大容量，低背景，测试设施低温恒温器将用于研究光谱仪的关键组件的光学和热性能，例如eTalons，机制和计量。评估在低温温度下综合系统性能的能力将使加拿大成为未来FIR空间天文学任务中首选的合作伙伴。******