基于Gaia XP光谱得到的Vera C. Rubin LSST合成星等
Vera C. Rubin LSST Synthetic Magnitudes derived from Gaia XP Spectra
AI总结：
本文开发了基于SDSS Stripe 82测光校正Gaia XP光谱的方法，得到的LSST合成测光残差大幅降低，可支撑Gaia与LSST数据的联合分析以研究银河系相关问题。
AI中文摘要：
背景：在银河系研究领域，Vera C. Rubin天文台的空间和时间遗产巡天（LSST）常被描述为Gaia巡天的深度扩展。未来对Gaia与LSST数据的联合分析有望为理解银河系结构与形成历史带来新见解，但两项巡天星等范围的重叠度相对较小，引发了如何对这些数据集进行联合定标的问题。目标：本文利用SDSS和DES观测得到的测光数据对Gaia XP低分辨率光谱进行定标，生成高质量的LSST合成测光。方法：开发了一种使用SDSS Stripe 82测光对Gaia XP光谱进行经验校正的方法，将拥有Gaia XP数据的源投影到星等-星等网格上，计算未校正合成星等与观测SDSS星等之间的残差，再利用这些残差推导对应各测光波段的光谱区域的校正系数。结果：该校正显著降低了合成星等中的系统趋势与离散度：残差中位数降低了一个数量级（例如u波段的改善从0.038 mag降至0.002 mag），残差标准差通常缩小至原来的二分之一（例如u波段从0.2 mag降至0.07 mag）。结论：本文的校正方法提高了从Gaia XP光谱得到的合成测光的可靠性，可支持Gaia与LSST数据的联合分析，用于银河系结构与恒星族的研究。
英文摘要：
Context. In the context of Milky Way studies, the Vera C. Rubin Observatory's Legacy Survey of Space and Time is often described as a deep extension of the Gaia survey. In the future, joint analysis of the Gaia and LSST data promises to bring new insights into our understanding of the Galaxy's structure and formation history. However, the relatively small overlap in the magnitude ranges of the two surveys raises the question of how to perform a joint calibration of these datasets. Aims. In this paper, we produce high-quality synthetic LSST photometry from Gaia XP low-resolution spectra, using SDSS and DES observed photometry to calibrate the spectra. Methods. We develop a method of empirical correction of Gaia XP spectra using SDSS Stripe 82 photometry. We project sources for which Gaia XP data are available onto a magnitude-magnitude grid and calculate residuals between uncorrected synthetic and observed SDSS magnitudes, which are then used to derive correction coefficients across spectral regions corresponding to each photometric band. Results. The correction significantly reduces systematic trends and scatter in the synthetic magnitudes: the median residuals decrease by an order of magnitude (e.g., for the u band the improvement is from 0.038 to 0.002 mag), and the standard deviation of residuals typically becomes up to factor of two smaller (e.g., for the u band from 0.2 to 0.07 mag). Conclusions. Our correction approach improves the reliability of synthetic photometry derived from Gaia XP spectra and enables joint analysis of Gaia and LSST data for studies of Galactic structure and stellar populations.
