NII和H $α$线混合对WFIRST星系红移巡天的影响
Effects of NII and H$α$ Line Blending on the WFIRST Galaxy Redshift Survey
摘要：
宽视场红外巡天望远镜（WFIRST）将使用H $α$发射线进行星系红移巡天，主要用于光谱红移测定。由于棱镜的光谱分辨率适中，H $α$和邻近的[NII]线混合在一起，导致红移偏差取决于[NII]/H $α$的比率，这与星系的金属丰度相关，因此质量和最终环境。我们调查这种偏见如何传播到星系团和宇宙学参数从WFIRST。利用模拟，我们探讨了谱线混合对红移空间畸变和重子声振荡（BAO）测量的影响。我们测量了BAO参数$α_{\parallel}$、$α_{\perp}$和对数生长因子$f_{v}$，并根据线比与大尺度结构之间的相关性计算了它们的误差。对于红移1.355- 1.994（0.700- 1.345），我们发现了$Δα_{\parallel} = 0.31 \pm 0.23 \%$（$0.26\pm0.17\%$）、$Δα_{\perp} = -0.10\pm0.10\%$（$-0.12 \pm 0.11 \%$）和$Δf_{v} = 0.17\pm0.33\%$（$-0.20 \pm 0.30\%$），它们在平方根和意义上使用了大约18 $\%$、9 $\%$和7 $\%$的系统误差预算。这些错误可能已经可以容忍，但讨论了进一步的缓解措施。由于环境无关的红移误差的偏差可以减轻测量的红移误差概率分布函数。需要对几千个星系进行高光谱分辨率的重新观测（如果是直接观测的话），以将它们的误差预算减少到25 $\%$以下。最后，我们概述了下一步改进[NII]引起的混合偏差及其与其他红移误差源的相互作用的建模。
英文摘要：
The Wide Field Infrared Survey Telescope (WFIRST) will conduct a galaxy redshift survey using the H$α$ emission line primarily for spectroscopic redshift determination. Due to the modest spectroscopic resolution of the grism, the H$α$ and the neighboring [NII] lines are blended, leading to a redshift bias that depends on the [NII]/H$α$ ratio, which is correlated with a galaxy's metallicity, hence mass and ultimately environment. We investigate how this bias propagates into the galaxy clustering and cosmological parameters obtained from the WFIRST. Using simulation, we explore the effect of line blending on redshift-space distortion and baryon acoustic oscillation (BAO) measurements. We measure the BAO parameters $α_{\parallel}$, $α_{\perp}$, the logarithmic growth factor $f_{v}$, and calculate their errors based on the correlations between the line ratio and large-scale structure. We find $Δα_{\parallel} = 0.31 \pm 0.23 \%$ ($0.26\pm0.17\%$), $Δα_{\perp} = -0.10\pm0.10\%$ ($-0.12 \pm 0.11 \%$), and $Δf_{v} = 0.17\pm0.33\%$ ($-0.20 \pm 0.30\%$) for redshift 1.355--1.994 (0.700--1.345), which use approximately 18$\%$, 9$\%$, and 7$\%$ of the systematic error budget in a root-sum-square sense. These errors may already be tolerable but further mitigations are discussed. Biases due to the environment-independent redshift error can be mitigated by measuring the redshift error probability distribution function. High-spectral-resolution re-observation of a few thousand galaxies would be required (if by direct approach) to reduce them to below 25$\%$ of the error budget. Finally, we outline the next steps to improve the modeling of [NII]-induced blending biases and their interaction with other redshift error sources.
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。
