标题： 利用 DESI-Y1 数据，追溯从红移 z=0.75 到 z=1.65 期间 CGM 和 IGM 环境中冷气体的演化，通过 Mg II 吸收研究 显示英文标题

标题： Tracing the evolution of the cool gas in CGM and IGM environments through Mg II absorption from redshift z=0.75 to z=1.65 using DESI-Y1 data

摘要： 我们测量了由Mg II（${\lambda\lambda 2796, 2803}$）追踪的冷气体在发射线星系（ELGs）周围的平均吸收情况，空间尺度从20千秒差距到10兆秒差距。该测量基于将大约250万个ELGs在$z = 0.75-1.65$处的位置与来自暗能量光谱仪（DESI）第一年样本提供的140万颗背景类星体光谱中的金属吸收特征进行交叉匹配。这些ELGs被分为两个红移区间：$0.75 < z < 1.0$和$1.0 < z < 1.65$。我们发现，通过堆叠ELG-QSO对构建的复合光谱显示出随红移的变化趋势，其中$z>1$具有系统性更高的Mg II吸收信号。在1兆秒差距范围内，$z > 1$的冷气体覆盖分数高于$z < 1$。 增强效应变得不那么明显，特别是在投影距离达到$r_{p}>$1 Mpc 时。 此外，具有更高恒星质量和恒星形成率（SFR）的电离发射线星系（ELGs）在$z<1$处产生更高的Mg II吸收体聚类。对于$z>1$，不同SFR的覆盖分数几乎没有差异。 更高红移处的Mg II吸收也支持宇宙正午时期更高的恒星形成观测结果。 此外，Mg II吸收轮廓在大约1 Mpc的尺度上显示出斜率的变化，这与从暗物质晕主导环境过渡到由晕-晕相关性主导的环境的预期一致。 我们估计了冷气体密度分布，并推导出不同红移处的金属丰度。 金属丰度的增长表明，在更高的红移处，星系际介质（IGM）中冷气体的存在有所增加。 显示英文摘要

摘要： We present a measurement of the mean absorption of cool gas traced by Mg II (${\lambda\lambda 2796, 2803}$) around emission line galaxies (ELGs), spanning spatial scales from 20 kpc to 10 Mpc. The measurement is based on cross-matching the positions of about 2.5 million ELGs at $z = 0.75-1.65$ and the metal absorption in the spectra of 1.4 million background quasars with data provided by the Year 1 sample of the Dark Energy Spectroscopic Instrument (DESI). The ELGs are divided into two redshift intervals: $0.75 < z < 1.0$ and $1.0 < z < 1.65$. We find that the composite spectra constructed by stacking the ELG-QSO pairs show evolution with redshift, with $z>1$ having a systematically higher signal of Mg II absorption. Within 1 Mpc, the covering fraction of the cool gas at $z > 1$ is higher than that of $z < 1$. The enhancement becomes less apparent especially if the projected distance $r_{p}>$1 Mpc. Also, ELGs with higher stellar mass and star formation rate (SFR) yield higher clustering of Mg II absorbers at $z<1$. For $z>1$, the covering fractions with different SFRs show little difference. The higher Mg II absorption at higher redshift also supports the observations of higher star formation at cosmic noon. Besides, the profile of Mg II absorption reveals a change of slope on scales of about 1 Mpc, consistent with the expected transition from a dark matter halo-dominated environment to a regime where clustering is dominated by halo-halo correlations. We estimate the cool gas density profile and derive the metal abundance at different redshifts. The growth of metal abundance suggests an increased presence of cool gas in the intergalactic medium (IGM) towards higher redshifts.