Data Tables for Enrichment by Extragalactic First Stars in the Large Magellanic Cloud
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Machine-readable data tables for the article, "Enrichment by Extragalactic First Stars in the Large Magellanic Cloud"-- DOI: 10.1038/s41550-024-02223-w. Full descriptions of the tables are in the article, but we briefly summarize here- Table 1 (Table1.csv): This table provides general information on the stars for which we obtained long-exposure Magellan/MIKE data to derive their detailed elemental abundances. Columns include names, coordinates, SkyMapper g magnitudes from the Gaia XP spectra, and stellar parameters and metallicities with their respective random uncertainties. Table 2 (Table2.csv): This table provides names, radial velocities, metallicities, and selected elemental abundances with random uncertainties for stars listed in Table 1. [C/Fe]_c indicates carbon abundances that are corrected for the evolutionary state of the star following Placco et al. (2014). Abundances that are upper limits are flagged by the ul_[X/Fe] columns and have "nan" values for the uncertainty. Extended Data Table 1 (Extended_Data_Table1.csv): This table summarizes all of our observations, by providing names, coordinates, SkyMapper g magnitudes from the Gaia XP spectra, exposure times, dates of observation, and the instrument for these observations. This table includes stars observed with MagE, those observed with short-exposures with MIKE for just metallicities and carbon abundances, and those flagged as more metal-rich upon initial exposure and hence, not further observed. Extended Data Table 2 (Extended_Data_Table2.csv): This table provides names, followed by stellar parameters, metallicities, and carbon abundances, along with their respective uncertainties, for stars observed with MagE or MIKE for short exposures to just obtain a metallicity and carbon abundance. As in Table 2, abundances that are upper limits are flagged by the ul_[C/Fe] column and "nan" entries for the uncertainty. Supplementary Data 1 (Summary_Data_1.csv or Summary_Data_1.ascii): This table provides the suite of detailed element abundances and uncertainties from the long-exposure MIKE spectra of the stars in Table 1. Columns include the name, atomic number and ionization state of the element (element), the number of features used to estimate the elemental abundance (N), the solar abundance of that element (Solar), the absolute abundance (logeps), the chemical abundance scaled by the solar abundance relative to hydrogen ([X/H]), the ratio with respect to the iron abundance ([X/Fe]), the random uncertainty ([X/H]_err) and an upper limit flag (ul), and errors from propagating the uncertainties in the individual stellar parameters and the overall systematic and total uncertainty ([X/H]_errteff, [X/H]_errlogg, [X/H]_errvt, [X/H]_errsys, [X/H]_errtot). These are followed by the same columns, but with respect to iron (e.g., [X/Fe]_errteff, [X/Fe]_errlogg). Abundances of the CH molecule are indicated by 106.0 in the "element" column. This table is provided as a machine readable csv file and as an ascii file, the latter for easier visual readability. Supplementary Data 2 (Summary_Data_2.csv or Summary_Data_2.ascii): This table summarizes the chemical abundances from individual absorption features for the LMC stars with long-exposure MIKE spectra. The columns include the star name, the atomic number and ionization state of the element (species), the solar abundance of that element (Solar), followed by the wavelength, excitation potential, and loggf of the line (wavelength, expot, loggf), and then the measured equivalent width (EW), absolute abundance (logeps), and a flag indicating whether the abundance is an upper limit (ul). Abundances derived via spectral synthesis have "nan" entries for expot, loggf, and EW, and abundances of the CH molecular band are indicated by 106.0. This table is provided as a machine readable csv file and as an ascii file, the latter for easier visual readability.
本数据集为论文《河外第一代恒星在大麦哲伦星系中的元素富集》（DOI: 10.1038/s41550-024-02223-w）配套的机器可读数据表。论文已完整说明各数据表的细节，此处仅作简要概述： 表1（Table1.csv）：本数据表收录了我们通过长曝光Magellan/MIKE光谱获取详细元素丰度的恒星的基础信息，列项包含恒星名称、天球坐标、基于Gaia XP光谱得到的SkyMapper g星等，以及恒星参数、金属丰度及其对应随机不确定度。 表2（Table2.csv）：本数据表收录了表1中恒星的名称、视向速度、金属丰度、选定元素丰度及其随机不确定度。其中[C/Fe]_c表示经Placco等（2014）校正恒星演化状态后的碳丰度。作为上限值的丰度会通过ul_[X/Fe]列标记，且其不确定度值为"nan"。 扩展数据表1（Extended_Data_Table1.csv）：本数据表汇总了全部观测项目，包含恒星名称、天球坐标、基于Gaia XP光谱得到的SkyMapper g星等、曝光时长、观测日期以及所用观测仪器。本数据表涵盖三类恒星：使用MagE开展观测的恒星、仅通过MIKE短曝光光谱获取金属丰度与碳丰度的恒星，以及在初始观测中被判定为金属丰度较高因而未进行后续观测的恒星。 扩展数据表2（Extended_Data_Table2.csv）：本数据表收录了通过MagE或MIKE短曝光观测、仅获取金属丰度与碳丰度的恒星的名称、恒星参数、金属丰度、碳丰度及其对应不确定度。与表2一致，作为上限值的丰度会通过ul_[C/Fe]列标记，且其不确定度值为"nan"。 补充数据1（Summary_Data_1.csv 或 Summary_Data_1.ascii）：本数据表提供了表1中恒星长曝光MIKE光谱对应的全套详细元素丰度及其不确定度。列项依次为：恒星名称、元素的原子序数与电离态（element列）、用于估算元素丰度的谱线数量（N）、该元素的太阳丰度（Solar）、绝对丰度（logeps）、以太阳丰度为标度、相对于氢的化学丰度比值（[X/H]）、相对于铁丰度的比值（[X/Fe]）、随机不确定度（[X/H]_err）以及上限标记（ul）；同时包含由恒星参数误差传播得到的不确定度与整体系统误差、总不确定度（[X/H]_errteff、[X/H]_errlogg、[X/H]_errvt、[X/H]_errsys、[X/H]_errtot）。后续列则为相对于铁丰度的对应误差项（如[X/Fe]_errteff、[X/Fe]_errlogg等）。CH分子的丰度会在"element"列中以106.0标记。本数据表同时提供机器可读的csv格式与便于目视查阅的ascii格式。 补充数据2（Summary_Data_2.csv 或 Summary_Data_2.ascii）：本数据表汇总了拥有长曝光MIKE光谱的大麦哲伦星系恒星的单条吸收谱线化学丰度。列项依次为：恒星名称、元素的原子序数与电离态（species列）、该元素的太阳丰度（Solar），随后是谱线的波长、激发势与loggf值（wavelength、expot、loggf），接着为测得的等效宽度（EW）、绝对丰度（logeps）以及标记丰度是否为上限值的标志（ul）。通过光谱合成得到的丰度，其expot、loggf与EW值为"nan"；CH分子带的丰度会以106.0标记。本数据表同时提供机器可读的csv格式与便于目视查阅的ascii格式。
