哈勃空间望远镜关于半人马座ω的大型计划——VII. 白矮星冷却序
The HST Large Programme on Omega Centauri -- VII. The white dwarf cooling sequence
AI总结：
本研究利用HST观测分析半人马座ω的白矮星冷却序与光度函数，确定其终止端峰值，并探讨单一年龄与长达50亿年年龄范围的可能性。
摘要：
我们提出了一项针对球状星团（GC）半人马座ω中白矮星（WD）冷却序（CS）的研究，这是一项专门的哈勃空间望远镜（HST）计划的主要目标。我们的分析揭示，WD CS终止端的峰值位于m_F606W=30.1±0.2（相当于V~31）。半人马座ω WD CS较亮的部分与大质量氦核WD的存在相一致，这与此前使用紫外和蓝色滤光片进行的HST分析吻合。将WD光度函数（LF）与理论对应物进行的比较分析表明，该星团的单一年龄星族与数据相容。然而，仅对WD LF的分析无法完全排除存在年龄范围的可能性，原因在于现今WD质量函数的不确定性；其恒星形成历史可能跨越长达50亿年，主要由约130亿年的恒星组成，仅有少数可能年轻至80亿年。这强调需要开展全局光谱和测光研究，同时纳入WD星族及其先前演化阶段，以充分理解该星团多样的化学成分和年龄。
英文摘要：
We present a study of the white dwarf (WD) cooling sequence (CS) in the globular cluster (GC) Omega Centauri, the primary goal of a dedicated Hubble Space Telescope (HST) programme. Our analysis has revealed that the peak at the termination of the WD CS is located at $m_{\rm F606W}$=30.1$\pm$0.2 (equivalent to $V$$\sim$31). The brighter part of Omega Centauri's WD CS is consistent with the presence of massive He-core WDs, in agreement with previous HST analyses with ultraviolet and blue filters. Comparative analyses of the WD luminosity function (LF) with theoretical counterparts have shown that a single-age population for the cluster is compatible with the data. However, an analysis of just the WD LF cannot entirely exclude the possibility of an age range, due to uncertainties in the present-day WD mass function, with a star formation history potentially spanning up to 5 billion years, predominantly comprising stars about 13 Gyr old, and with just a minority potentially as young as 8 Gyr. This underscores the need for global spectroscopic and photometric investigations that include simultaneously the WD populations together with the previous evolutionary phases to fully understand the cluster's diverse chemical compositions and ages.
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