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arXiv 2010.14005astro-ph.IMastro-ph.SR
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基于恒星的中国空间站望远镜(CSST)无狭缝光谱巡天精密波长定标方法

A Star-based Method for Precise Wavelength Calibration of the Chinese Space Station Telescope (CSST) Slitless Spectroscopic Survey

Haibo Yuan, Dingshan Deng, Yang Sun

摘要:

中国空间站望远镜(CSST)光谱巡天的目标是为数亿个目标提供高质量的低分辨率($R > 200$)无狭缝光谱,这些目标的极限星等约为21等,分布在大的巡天区域(17500 deg $^2$)内,并覆盖宽的波长范围(255-1000 nm,3个波段GU,GV和GI)。由于无狭缝光谱学不使用波长校准灯,波长校准是无狭缝光谱缩减中最具挑战性的问题之一,但它在精确测量恒星径向速度和星系红移方面起着关键作用。在这项工作中,我们提出了一种基于恒星的方法,可以使用正常的科学观测来监测和校正CSST波长校准中可能存在的误差,利用以下事实:i)由于像LAMOST这样的光谱测量,现在有大约1000万颗恒星具有可靠的径向速度,ii)CSST的大视场可以在短时间内有效地观测这些恒星,和iii)这样的恒星的径向速度可以可靠地测量使用只有一个狭窄的部分CSST光谱。我们证明,它是可能实现的波长校准精度的几个$\mathrm{km}\,\mathrm{s}^{-1}$的GU波段,约10至20 $\mathrm{km}\,\mathrm{s}^{-1}$的GV和GI波段,只有几百个速度标准星。本文还讨论了该方法在其他调查中的应用。

英文摘要:

The Chinese Space Station Telescope (CSST) spectroscopic survey aims to deliver high-quality low-resolution ($R > 200$) slitless spectra for hundreds of millions of targets down to a limiting magnitude of about 21 mag, distributed within a large survey area (17500 deg$^2$) and covering a wide wavelength range (255-1000 nm by 3 bands GU, GV, and GI). As slitless spectroscopy precludes the usage of wavelength calibration lamps, wavelength calibration is one of the most challenging issues in the reduction of slitless spectra, yet it plays a key role in measuring precise radial velocities of stars and redshifts of galaxies. In this work, we propose a star-based method that can monitor and correct for possible errors in the CSST wavelength calibration using normal scientific observations, taking advantage of the facts that i) there are about ten million stars with reliable radial velocities now available thanks to spectroscopic surveys like LAMOST, ii) the large field of view of CSST enables efficient observations of such stars in a short period of time, and iii) radial velocities of such stars can be reliably measured using only a narrow segment of CSST spectra. We demonstrate that it is possible to achieve a wavelength calibration precision of a few $\mathrm{km}\,\mathrm{s}^{-1}$ for the GU band, and about 10 to 20 $\mathrm{km}\,\mathrm{s}^{-1}$ for the GV and GI bands, with only a few hundred velocity standard stars. Implementations of the method to other surveys are also discussed.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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