A NEW DISTANCE TO M33 USING BLUE SUPERGIANTS AND THE FGLR METHOD
A NEW DISTANCE TO M33 USING BLUE SUPERGIANTS AND THE FGLR METHOD
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使用蓝超巨星和 FGLR 方法计算到 M33 的新距离
DOI：
10.1088/0004-637x/704/2/1120
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
N. Przybilla
中科院分区：
文献类型：
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作者：
V. U;M. Urbaneja;R. Kudritzki;B. Jacobs;F. Bresolin;N. Przybilla
用凯克望远镜的DEIMOS和ESI对A和B超巨星的中等分辨率光谱进行定量光谱分析，确定三角座星系M33的距离模为24.93 ± 0.11等（968 ± 50千秒差距）。分析产生恒星的有效温度，重力，星际红化和消光，其组合提供了一个距离估计通过通量加权的重力-光度关系（FGLR）。这一结果是基于不断完善的FGLR校准。平均红化的α E（B − V）为0.08等，变化范围从0.01到0.16等，然而，证明了在具有明显星际吸收特征的星系中精确的个体红化测量对于恒星距离指标的重要性。发现的大距离模量与最近的食双星，行星状星云，长周期变星，RR天琴座恒星的工作，也与哈勃太空望远镜（HST）的观测造父变星，如果合理的红化假设造父变星是在很好的协议。由于在文献中发现的基于红巨星分支尖端（TRGB）方法的距离给出了相互矛盾的结果，我们使用HST高级巡天照相机测量M33外部区域的V-和I-波段图像来确定TRGB距离为24.84 ± 0.10等，与FGLR结果基本一致。我们还测定了恒星金属丰度，并讨论了M33盘的金属丰度梯度。在等照度线半径处，中心的金属丰度为Z尖，边缘的金属丰度为0.3 Z尖。金属丰度的平均对数梯度为−0.07 ± 0.01 dex kpc−1。然而，在这个平均值周围有一个很大的分散，非常类似于在M33中的H ii区域所发现的。
The quantitative spectral analysis of medium resolution optical spectra of A and B supergiants obtained with DEIMOS and ESI at the Keck Telescopes is used to determine a distance modulus of 24.93 ± 0.11 mag (968 ± 50 kpc) for the Triangulum Galaxy M33. The analysis yields stellar effective temperatures, gravities, interstellar reddening, and extinction, the combination of which provides a distance estimate via the flux-weighted gravity–luminosity relationship (FGLR). This result is based on an FGLR calibration that is continually being polished. An average reddening of 〈E(B − V)〉 ∼ 0.08 mag is found, with a large variation ranging from 0.01 to 0.16 mag, however, demonstrating the importance of accurate individual reddening measurements for stellar distance indicators in galaxies with evident signatures of interstellar absorption. The large-distance modulus found is in good agreement with recent work on eclipsing binaries, planetary nebulae, long-period variables, RR Lyrae stars, and also with Hubble Space Telescope (HST) observations of Cepheids, if reasonable reddening assumptions are made for the Cepheids. Since distances based on the tip of the red giant branch (TRGB) method found in the literature give conflicting results, we have used HST Advanced Camera for Surveys V- and I-band images of outer regions of M33 to determine a TRGB distance of 24.84 ± 0.10 mag, in basic agreement with the FGLR result. We have also determined stellar metallicities and discussed the metallicity gradient in the disk of M33. We find metallicity of Z☉ at the center and 0.3 Z☉ in the outskirts at a distance of one isophotal radius. The average logarithmic metallicity gradient is −0.07 ± 0.01 dex kpc−1. However, there is a large scatter around this average value, very similar to what has been found for the H ii regions in M33.