AI 中文总结
研究将SPISEA恒星群体合成框架扩展到亚恒星领域，通过实施现代初始质量函数、引入合并大气网格等方法，经与多星团观测数据验证，新模型可重现恒星行为并适用于亚恒星科学案例及奠定未来相关基础。
AI 中文摘要
我们展示了SPISEA恒星群体合成框架的扩展，将褐矮星添加到现有的恒星质量对象范围内，从而能够在合成星团中对褐矮星进行物理上一致的建模。以前版本的SPISEA对亚恒星的支持有限，依赖过时的初始质量函数以及氢燃烧极限以下不完整的大气和演化覆盖。通过基于可靠观测约束实施现代亚恒星初始质量函数、引入在恒星和褐矮星区域之间平滑过渡的合并大气网格以及构建跨越从最低质量褐矮星到太阳金属丰度大质量恒星的统一演化轨迹来解决此问题。通过将模拟的颜色-星等图与昴宿星团、天蝎座上部和M44星团使用盖亚、UKIDSS和2MASS测光的观测数据进行比较，验证了更新后的框架。新模型允许生成用户指定的等时线和星团，既能重现观测到的恒星行为，又能在褐矮星领域进行现实的群体合成。这项工作扩展了SPISEA在亚恒星科学案例中的适用性，包括年轻星团研究和微透镜模拟，并为未来纳入行星质量对象和非太阳金属丰度奠定了基础。
英文摘要
We present an extension of the SPISEA stellar population synthesis framework that adds brown dwarfs to the existing range of stellar mass objects, enabling physically consistent modeling of brown dwarfs within synthetic star clusters. Previous versions of SPISEA included limited substellar support, relying on outdated initial mass functions and incomplete atmospheric and evolutionary coverage below the hydrogen-burning limit. This was addressed through the implementation of a modern substellar initial mass function based on robust observational constraints, the introduction of merged atmospheric grids that smoothly transition between stellar and brown dwarf regimes, and the construction of unified evolutionary tracks spanning the lowest-mass brown dwarf objects through massive stars at solar metallicity. The updated framework was validated by comparing simulated color-magnitude diagrams to observational data from the Pleiades, Upper Scorpius, and M44 clusters using Gaia, UKIDSS, and 2MASS photometry. The new models allow for generation of user-specified isochrones and clusters that reproduce observed stellar behaviors while enabling realistic population synthesis in the brown dwarf regime. This work extends SPISEA's applicability to substellar science cases, including young cluster studies and microlensing simulations, and provides a foundation for future incorporation of planetary-mass objects and non-solar metallicities.
Comments18 pages, 12 figures, submitted to The Astrophysical Journal
