AI 中文总结
研究银河系矮球状卫星的结构多样性，通过灵活的双幂律模型拟合恒星密度场，发现其种群有多样密度剖面形状，该模型使半光半径和恒星质量估计更不确定，强调密度剖面形状灵活性对dSph质量建模很关键。
AI 中文摘要
我们将灵活的双幂律（`$\alpha\beta\gamma$'）模型应用于银河系已知矮球状卫星星系观测到的恒星密度场。结果表明，在模型选择标准起决定性作用的情况下，$\alpha\beta\gamma$模型比普卢默模型的特殊情况、sersic模型及其特殊情况指数模型更受青睐。银河系的dSph种群呈现出多样的恒星密度剖面形状，通过推断的外幂律指数$\beta$和内幂律指数$\gamma$值来量化。一些质量最大的dSph（如波江座II、天炉座、狮子座I、狮子座II）具有陡峭下降的外剖面，$\beta\gtrsim 8$；其他的（如六分仪座、牧夫座I）则衰减缓慢，$\beta\lesssim 4$。恒星质量$\gtrsim 10^5 M_{\odot}$的dSph的内剖面与均匀恒星密度的“核心”一致（$\gamma\approx 0$）。在较低质量下，内密度剖面的斜率约束较差，除了少数超暗弱dSph（如武仙座、大熊座II），我们推断其有陡峭的恒星尖峰，$\gamma\gtrsim 1.5$。由于$\alpha\beta\gamma$模型的灵活性，推断的半光半径和总恒星质量比以前的估计更不确定，在某些情况下半光半径大一个数量级。最后表明，允许恒星密度剖面形状具有灵活性对于dSph质量建模至关重要，其中与恒星密度剖面选择相关的系统误差可能超过观测速度弥散中的随机误差。
英文摘要
We fit a flexible double power-law (`$αβγ$') model to the stellar density fields observed for the Milky Way's known dwarf spheroidal satellite galaxies. We show that where standard criteria for model selection are decisive, the $αβγ$ model is favored over the special case of the Plummer model, and also over the \sersic\ model and its special case, the exponential. The Milky Way's dSph population exhibits a diverse range of stellar density profile shapes, as quantified by the values we infer for outer and inner power-law indices $β$ and $γ$. Several of the most massive dSphs (e.g., Eridanus II, Fornax, Leo I, Leo II) have steeply-declining outer profiles, with $β\gtrsim 8$; others (e.g., Sextans, Boötes I) fade slowly, with $β\lesssim 4$. The inner profiles of dSphs with stellar mass $\gtrsim 10^5 M_{\odot}$ are consistent with `cores' of uniform stellar density ($γ\approx 0$). At lower masses the slopes of inner density profiles are poorly constrained, except in a few ultrafaint dSphs (e.g., Hercules, Ursa Major II) where we infer steep stellar cusps, with $γ\gtrsim 1.5$. Owing to the $αβγ$ model's flexibility, the inferred halflight radii and total stellar masses are significantly more uncertain than previous estimates, with halflight radii larger by up to an order of magnitude in some cases. Finally, we demonstrate that allowing for flexibility in the shape of the stellar density profile is crucial for dSph mass modeling, where systematic errors associated with choice of stellar density profile can outweigh random errors in the observed velocity dispersions.
Commentsto be submitted. Supporting files (input catalogs, samples from posterior PDFs, figures for all galaxies) are available at https://doi.org/10.5281/zenodo.20600394
