中国科学院云南天文台学术报告通知

2025年第20期

报告题目：Bridging the scales: an analytical model for Population III star formation

报告人：刘博远（Boyuan Liu） 博士后

报告人单位：海德堡大学天文学中心 (Centre for Astronomy of Heidelberg University)

报告语言：中文/English

报告时间：6月20日（星期五）10:30-11:30

报告地点：一号楼412会议室

报告摘要：

～～～～～～～～～～～～～

The first generation of so-called Population III (Pop III) stars, formed in extremely metal-poor primordial gas with inefficient cooling, are expected to have distinct features compared with present-day metal-enriched stars (more massive, compact, and less mass loss) and play important roles in the first billion years of cosmic history through their radiation, metal enrichment, and by seeding massive black holes (BHs). Although their detailed properties are largely unknown, direct and indirect probes (e.g., galaxy surveys by JWST, stellar archaeology, binary BH mergers, and 21-cm signal) are providing us with increasingly more clues. Self-consistent theoretical predictions of the formation rates, sites, and masses of Pop III stars are crucial for interpreting observations, but are challenging due to complex physical processes operating over the large range of length scales involved. One solution is to combine analytical models for the small-scale star formation process with cosmological simulations that capture the large-scale physics, such as structure formation, radiation backgrounds, and baryon-dark matter streaming motion that regulate the conditions of Pop III star formation. To bridge the scales, we build an analytical model to predict the final masses of Pop III stars/clusters from the properties of star-forming clouds, based on the key results of small-scale star formation simulations and stellar evolution models. Our model for the first time considers the interplay between feedback and fragmentation and covers different modes of Pop III star formation ranging from ordinary small (~10 − 2000 solar masses) clusters in molecular-cooling clouds to massive (> 10^4 Msun) clusters containing supermassive (~10^4 − 3x10^5 Msun) stars under violent collapse of atomic-cooling clouds with large gas accretion rates of > 0.1 Msun/yr. As an example, the model is applied to the Pop III star-forming clouds in the progenitors of typical haloes hosting high-redshift luminous quasars (M~10^12 Msun at z~6), which shows that formation of Pop III massive clusters is common (~20-70%) in such biased (~4 sigma) regions, and the resulting heavy black hole seeds from supermassive stars can account for a significant fraction of observed luminous (> 10^46 erg/s) quasars at z~6.

～～～～～～～～～～～～～

报告人简介： 

Boyuan Liu is a postdoc at the Center for Astronomy of Heidelberg University (ZAH) working in the group of Prof. Michela Mapelli as part of the Excellence Cluster STRUCTURES program. Before moving to Heidelberg, he was a postdoc at the Institute of Astronomy, University of Cambridge from 2022 to 2024, working with Prof. Anastasia Fialkov.

He gained my PhD degree from the University of Texas at Austin with the mentorship of Prof. Volker Bromm. He use semi-analytical models and numerical simulations to predict the properties of the first generation of stars, black holes, star clusters, and galaxies in the Universe, to shed light on their roles in early cosmic evolution and unique signatures in multi-messenger observations (e.g., star formation histories and galaxy metal scaling relations of high-z galaxies, the 21-cm signal from neutral hydrogen, reionization, gravitational waves from compact object mergers, abundance patterns of metal-poor stars/nebulae, seeding and growth of supermassive black holes).

邀请方：大样本恒星演化研究团组、国际超新星中心、云南省国际超新星研究重点实验室

联系人：柳正伟