A Step toward the Calibration of the Red Giant Branch Tip as a Standard Candle
A Step toward the Calibration of the Red Giant Branch Tip as a Standard Candle
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将红巨星分支尖端校准为标准蜡烛的一步
DOI：
10.1086/321613
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
E. Pancino
中科院分区：
文献类型：
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作者：
M. Bellazzini;F. Ferraro;E. Pancino
红巨星分支（M）尖端的绝对 I 星等是天体物理学中最有前途的标准烛光之一，实际上用作宇宙距离尺度的基本支柱。为了改善其校准的观测基础，我们获得了球状星团 ω Centauri 的 M 的准确估计，基于（1）由 Pancino 和同事为球状星团组装的最大光度数据库，以及（2）根据 Thompson 和同事最近从一个分离的食双星获得的 ω Cen 的直接距离估计。目前，导出值 M = -4.04 ± 0.12 提供了最准确的经验零点，用于校准 ~ -1.7 的 M 关系。我们还根据 Ferraro 及其同事最近提出的银河球状星团中红巨星的大型红外数据集推导了一种新的经验 M-[Fe/H] 关系。该数据库（扩展至 [Fe/H] = -0.2）比之前的经验校准（仅限于 [Fe/H] ≤ -0.7）涵盖了更适合河外应用的金属丰度范围。所提出的关系与新确定的零点非常一致。
The absolute I magnitude of the tip of the red giant branch (M) is one of the most promising standard candles actually used in astrophysics as a fundamental pillar for the cosmological distance scale. With the aim of improving the observational basis of its calibration, we have obtained an accurate estimate of the M for the globular cluster ω Centauri, based (1) on the largest photometric database ever assembled for a globular cluster, by Pancino and colleagues, and (2) on a direct distance estimate for ω Cen, recently obtained by Thompson and colleagues from a detached eclipsing binary. The derived value M = -4.04 ± 0.12 provides, at present, the most accurate empirical zero point for the calibration of the M- relation at ~ -1.7. We also derive a new empirical M-[Fe/H] relation based on the large IR data set of red giants in Galactic globular clusters recently presented by Ferraro and colleagues. This database (extending up to [Fe/H] = -0.2) covers a more appropriate metallicity range for extragalactic applications than previous empirical calibrations (which were limited to [Fe/H] ≤ -0.7). The proposed relation is in excellent agreement with the newly determined zero point.