南洋杉计划从宽视场成像巡天发现的造父变星到Local Group星系WLM的距离
The Araucaria Project. The Distance to the Local Group Galaxy WLM from Cepheid Variables discovered in a Wide-Field Imaging Survey
摘要：
我们对本星系群不规则星系WLM中的造父变星进行了广泛的宽视场成像观测。从101个夜晚获得的数据中，我们发现了60颗造父变星，其中包括Sandage和Carlson先前发现的15颗造父变星中的14颗。在3天的时间内，我们在WLM的Cepheid调查应该基本完成。重要的是，我们首次在这个星系中发现了一个长周期的造父变星（P=54.2天），缓解了WLM及其许多蓝色大质量恒星不包含周期超过10天的造父变星的困惑。我们的数据定义了V，I和无红化的Wesenchman星等${\rm W}_{\rm I}$的紧密周期光度关系，它们都非常好地拟合了LMC造父变星PL关系的相应斜率，表明PL关系斜率没有变化到造父变星金属丰度约为-1.0 dex，与最近的其他研究一致。我们从我们的数据中得出了WLM的真实距离模量为25.144 $\pm$ 0.03（r）$\pm$ 0.07（s）mag，与Lee，Freedman和Madore（1993 a）根据造父变星测定的24.92 $\pm$ 0.21 mag非常一致。引用的系统不确定度值不包括LMC距离的贡献，我们假设LMC距离为18.50等，如我们项目中以前的论文所述。
英文摘要：
We have conducted an extensive wide-field imaging survey for Cepheid variables in the Local Group irregular galaxy WLM. From data obtained on 101 nights, we have discovered 60 Cepheids which include 14 of the 15 Cepheid variables previously detected by Sandage and Carlson. Down to a period of 3 days, our Cepheid survey in WLM should be practically complete. Importantly, we have found for the first time a long-period Cepheid (P=54.2 days) in this galaxy, alleviating the puzzle that WLM with its many blue, massive stars does not contain Cepheids with periods longer than about 10 days. Our data define tight period-luminosity relations in V, I and the reddening-free Wesenheit magnitude ${\rm W}_{\rm I}$ which are all extremely well fit by the corresponding slopes of the LMC Cepheid PL relation, suggesting no change of the PL relation slope down to a Cepheid metal abundance of about -1.0 dex, in agreement with other recent studies. We derive a true distance modulus to WLM of 25.144 $\pm$0.03 (r) $\pm$0.07 (s) mag from our data, in good agreement with the earlier 24.92 $\pm$ 0.21 mag determination of Lee, Freedman and Madore (1993a) from Cepheid variables. The quoted value of the systematic uncertainty does not include the contribution from the LMC distance which we have assumed to be 18.50 mag, as in the previous papers in our project.
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