标题： 高精度宽带测光的力量：利用暗能量调查中的蓝水平分支恒星追踪银河系密度剖面 显示英文标题

标题： The Power of High Precision Broadband Photometry: Tracing the Milky Way Density Profile with Blue Horizontal Branch stars in the Dark Energy Survey

摘要： 蓝水平分支（BHB）恒星是探测银河系晕密度剖面的优秀距离示踪者，在$(g-r)_0$对$(i-z)_0$的颜色空间中，它们与另一类恒星——蓝离散星（BSs）区分开来。我们开发了一个贝叶斯混合模型，利用暗能量巡天数据发布2（DES DR2）的高精度测光数据对BHB恒星进行分类。我们根据其$griz$的测光数据和相关不确定性选择$\sim2100$个高概率的BHB恒星，并利用这些恒星在银心径向范围$20 \lesssim R \lesssim 70$kpc 内绘制恒星晕。 在排除已知的恒星过密度后，我们发现BHB的数密度$n_\star$可以用一个幂律密度分布$n_\star \propto R^{-\alpha}$来表示，指数为$\alpha=4.28_{-0.12}^{+0.13}$，这与现有文献值一致。 此外，我们检查了系统误差和空间非均匀性对拟合密度分布的影响。 我们的工作展示了高精度$griz$光度测量在选择BHB恒星方面的有效性。 来自鲁宾天文台的即将进行的光度巡天，预计在其10年任务期间将达到比DES深2-3个星等的深度，将使我们能够研究银河系晕的密度分布直至virial半径，揭示我们银河系形成和演化的复杂过程。 显示英文摘要

摘要： Blue Horizontal Branch (BHB) stars, excellent distant tracers for probing the Milky Way's halo density profile, are distinguished in the $(g-r)_0$ vs $(i-z)_0$ color space from another class of stars, blue straggler stars (BSs). We develop a Bayesian mixture model to classify BHB stars using high-precision photometry data from the Dark Energy Survey Data Release 2 (DES DR2). We select $\sim2100$ highly-probable BHBs based on their $griz$ photometry and the associated uncertainties, and use these stars to map the stellar halo over the Galactocentric radial range $20 \lesssim R \lesssim 70$ kpc. After excluding known stellar overdensities, we find that the number density $n_\star$ of BHBs can be represented by a power law density profile $n_\star \propto R^{-\alpha}$ with an index of $\alpha=4.28_{-0.12}^{+0.13}$, consistent with existing literature values. In addition, we examine the impact of systematic errors and the spatial inhomogeneity on the fitted density profile. Our work demonstrates the effectiveness of high-precision $griz$ photometry in selecting BHB stars. The upcoming photometric survey from the Rubin Observatory, expected to reach depths 2-3 magnitudes greater than DES during its 10-year mission, will enable us to investigate the density profile of the Milky Way's halo out to the virial radius, unravelling the complex processes of formation and evolution in our Galaxy.