Kavli Affiliate: Hu Zhan
| First 5 Authors: Jipeng Sui, Hu Zou, Xiaohu Yang, Xianzhong Zheng, Run Wen
| Summary:
The China Space Station Telescope (CSST) is a forthcoming space-based optical
telescope designed to co-orbit with the Chinese Space Station. With a planned
slitless spectroscopic survey spanning a broad wavelength range of $255-1000$nm
and an average spectral resolution exceeding 200, the CSST holds significant
potential for cosmic large-scale structure analysis. In this study, we focus on
redshift determinations from slitless spectra through emission line analysis
within the CSST framework. Our tailored redshift measurement process involves
identifying emission lines in one-dimensional slitless spectra, aligning
observed wavelengths with their rest-frame counterparts from prominent galaxy
emissions, and calculating wavelength shifts to determine redshifts accurately.
To validate our redshift measurement algorithm, we leverage simulated spectra
generated by the CSST emulator for slitless spectroscopy. The outcomes
demonstrate a remarkable redshift completeness exceeding 95 per cent for
emission line galaxies (ELGs), alongside a purity surpassing 85 per cent. The
redshift uncertainty remains impressively below than $sim 0.001$. Notably,
when concentrating on galaxies with more than three matched emission lines, the
completeness of ELGs and the purity of measurable galaxies can reach 98 per
cent and 97 per cent, respectively. Furthermore, we explore the influence of
parameters like magnitude, spectral signal-to-noise ratio, and redshift on
redshift completeness and purity. The discussion also delves into redshift
degeneracies stemming from emission-line matching confusion. Our developed
redshift measurement process will be applied to extensive simulated datasets
and forthcoming CSST slitless spectroscopic observations for further
cosmological and extragalactic analyses.
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