极低金属丰度O型星宝库
The Treasury of Extremely Metal-Poor O Stars
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中文总结 AI 辅助
TEMPOS项目利用哈勃望远镜获取极低金属丰度O型星的远紫外光谱，构建均匀观测图集，揭示恒星风速度与金属丰度的关系，为理解早期宇宙大质量恒星提供关键数据。
中文摘要 AI 辅助
极低金属丰度O型星宝库（TEMPOS）是一项哈勃太空望远镜巡天项目，旨在研究附近低金属丰度星系（金属丰度约为太阳金属丰度Z⊙的≤20%）中的炽热大质量O型星。理解该环境中的大质量恒星物理对于解释低金属丰度星系的观测至关重要，这些星系包括低质量矮星系和早期宇宙中化学演化未充分的星系。然而，在低于20% Z⊙的金属丰度下，目前仅有极少数质量足以表征其基本性质和恒星风的远紫外（FUV）光谱，且观测设计的不均匀性和参数空间覆盖的不完整性对研究进展构成了重大障碍。为解决这一问题，TEMPOS获得了12颗极低金属丰度O型星的新宇宙起源摄谱仪（COS）远紫外光谱，并结合档案数据，汇编了一个包含29颗均匀观测恒星的光谱图集，该图集有效覆盖了广泛的谱型和光度级。本文描述了TEMPOS的动机、样本选择和观测设计，并发布了首个经处理与合并的COS光谱数据版本。随后，我们展示了低于20% Z⊙的O型星远紫外光谱经验性质的首批结果，包括视向速度、光球谱线等值宽度和恒星风终端速度（v∞）。我们表明，v∞在约5%-50% Z⊙范围内与宿主星系金属丰度相关，并初步发现低于约10% Z⊙时恒星风强度下降更为陡峭的证据。结合远紫外光谱数据集以及TEMPOS宝库项目计划发布的光度数据和光学光谱，将增进我们对极低金属丰度环境下恒星天体物理学和星际介质的理解。
英文摘要
The Treasury of Extremely Metal-Poor O Stars (TEMPOS) is a Hubble Space Telescope survey of hot and massive O-type stars in nearby, low-metallicity galaxies ($\lesssim$20% of the solar metallicity, $Z_\odot$). Understanding massive-star physics in this regime is essential to interpret observations of metal-poor galaxies, including both low-mass dwarf galaxies and chemically unevolved galaxies in the early Universe. Yet, few far-ultraviolet (FUV) spectra of O stars of sufficient quality to characterize their fundamental properties and stellar winds exist below 20% $Z_\odot$, and heterogeneous observation design and incomplete coverage of parameter space pose significant barriers to progress. To remedy this, TEMPOS obtained new Cosmic Origins Spectrograph (COS) FUV spectra of 12 very metal-poor O stars, building upon archival data to assemble a spectroscopic atlas of 29 homogeneously observed stars that efficiently samples a wide range of spectral types and luminosity classes. Here, we describe the motivation, sample selection, and observation design for TEMPOS and present the first data release of reduced and coadded COS spectra. We then present initial results on the empirical properties of FUV O-star spectra below 20% $Z_\odot$, including radial velocities, equivalent widths of photospheric lines, and terminal wind velocities ($v_\infty$). We show that $v_\infty$ correlates with host galaxy metallicity across $\sim$5-50% $Z_\odot$ and find tentative evidence of a steeper decline in wind strength below $\sim$10% $Z_\odot$. The combined dataset of FUV spectra and planned releases of photometry and optical spectra from the TEMPOS Treasury program will advance our understanding of both stellar astrophysics and the interstellar medium in the extremely metal-poor regime.
发表机构
- University of Utah（犹他大学）
- Space Telescope Science Institute（太空望远镜科学研究所）
- Rutgers University（罗格斯大学）
- Christian-Albrechts-Universität zu Kiel（基尔大学）
- Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut（海德堡大学天文学计算中心）
- The University of Texas at Austin（德克萨斯大学奥斯汀分校）
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