Title: The DESI Y1 RR Lyrae catalog I: Empirical modeling of the cyclic variation of spectroscopic properties and a chemodynamical analysis of the outer halo Show Chinese title

Title: DESI Y1 RR Lyrae目录 I：光谱特性循环变化的经验建模和外晕的化学动力学分析

Abstract: We present the catalog of RR Lyrae stars observed in the first year of operations of the Dark Energy Spectroscopic Instrument (DESI) survey. This catalog contains 6,240 RR Lyrae stars out to $\sim100$\,kpc from the Galactic center and over 12,000 individual epochs with homogeneously-derived stellar atmospheric parameters. We introduce a novel methodology to model the cyclical variation of the spectroscopic properties of RR Lyrae from single-epoch measurements. We employ this method to infer the radial velocity and effective temperature variation of fundamental mode and first-overtone RR Lyrae stars and to determine their systemic velocities and mean temperatures. For fundamental mode pulsators, we obtain radial velocity curves with amplitudes of $\sim$30--50\,km\,s$^{-1}$ and effective temperature curves with 300--1,000\,K variations, whereas for first-overtone pulsators these amplitudes are $\sim20$\,km\,s$^{-1}$ and $\sim 600$\,K, respectively. We use our sample to study the metallicity distribution of the halo and its dependence on Galactocentric distance ($R_{\rm GC}$). Using a radius-dependent mixture model, we split the data into chemodynamically distinct components and find that our inner halo sample ($R_{\rm GC}\lesssim50$\,kpc) is predominantly composed of stars with [Fe/H] $\sim-1.5$\,dex and largely radial orbits (with an anisotropy parameter $\beta\sim0.94$), that we associate with the Gaia-Sausage-Enceladus merger event. Stars in the outer halo field exhibit a broader and more metal-poor [Fe/H] distribution with more circular orbits ($\beta\sim0.39$). The metallicity gradient of the metal-rich and the metal-poor components is found to be $0.005$ and $0.010$\,dex\,kpc$^{-1}$, respectively. Our catalog highlights DESI's tantalizing potential for studying the Milky Way and the pulsation properties of RR Lyrae stars in the era of large spectroscopic surveys. Show Chinese abstract

Abstract: 我们介绍了在暗能量光谱巡天仪器（DESI）调查第一年观测到的RR Lyr星的目录。 该目录包含6,240颗RR Lyr星，距离银河系中心最远为$\sim100$ kpc，并且有超过12,000个独立观测时刻，其恒星大气参数是均匀推导的。 我们引入了一种新方法，从单次观测中建模RR Lyr星的光谱特性周期性变化。 我们使用这种方法推断基频和第一泛音RR Lyr星的径向速度和有效温度变化，并确定它们的系统速度和平均温度。 对于基频脉动星，我们得到振幅为$\sim$30--50 km s$^{-1}$的径向速度曲线和300--1,000 K变化的有效温度曲线，而对于第一泛音脉动星，这些振幅分别为$\sim20$ km s$^{-1}$和$\sim 600$ K。 我们利用样本研究晕的金属丰度分布及其与银心距离（$R_{\rm GC}$）的关系。 使用基于半径的混合模型，我们将数据分为化学动力学上不同的成分，并发现我们的内晕样本（$R_{\rm GC}\lesssim50$kpc）主要由[Fe/H]$\sim-1.5$dex的恒星组成，且轨道主要为径向（各向异性参数为$\beta\sim0.94$），我们将其与Gaia-Sausage-Enceladus合并事件相关联。 外晕场中的恒星表现出更广泛且更贫金属的[Fe/H]分布，轨道更圆（$\beta\sim0.39$）。 富金属和贫金属成分的金属度梯度分别为$0.005$和$0.010$dex kpc$^{-1}$。 我们的星表突显了DESI在大规模光谱调查时代研究银河系以及RR天琴座变星脉动特性的诱人潜力。