标题： 哈勃太空望远镜河外距离尺度关键项目 XVII. NGC 4725的造父变星距离 显示英文标题

标题： The HST Key Project on the Extragalactic Distance Scale XVII. The Cepheid Distance to NGC 4725

摘要： 从造父变星得出到NGC 4725的距离，这是哈勃太空望远镜河外距离尺度关键项目的一部分。获得了十三个F555W（V）和四个F814W（I）周期的宇宙射线分裂宽视场和行星摄像机2观测数据。发现了二十颗造父变星，其周期范围从12天到49天。采用大麦哲伦云的距离模数和消光分别为18.50±0.10星等和E(V-I)=0.13星等，基于使用ALLFRAME软件包的分析，确定了NGC 4725的真实消光修正距离模数为30.50±0.16（随机）±0.17（系统）星等。对应的距离为12.6±1.0（随机）±1.0（系统）Mpc，与基于DoPHOT测光包的独立分析所得的距离非常一致。由于前景消光仅为E(V-I)=0.02，因此推断出的这个NGC 4725区域的固有消光E(V-I)=0.19，使其成为迄今为止HST关键项目中遇到的最高度消光的区域之一。 显示英文摘要

摘要： The distance to NGC 4725 has been derived from Cepheid variables, as part of the Hubble Space Telescope Key Project on the Extragalactic Distance Scale. Thirteen F555W (V) and four F814W (I) epochs of cosmic-ray-split Wide Field and Planetary Camera 2 observations were obtained. Twenty Cepheids were discovered, with periods ranging from 12 to 49 days. Adopting a Large Magellanic Cloud distance modulus and extinction of 18.50+/-0.10 mag and E(V-I)=0.13 mag, respectively, a true reddening-corrected distance modulus (based on an analysis employing the ALLFRAME software package) of 30.50 +/- 0.16 (random) +/- 0.17 (systematic) mag was determined for NGC 4725. The corresponding of distance of 12.6 +/- 1.0 (random) +/- 1.0 (systematic) Mpc is in excellent agreement with that found with an independent analysis based upon the DoPHOT photometry package. With a foreground reddening of only E(V-I)=0.02, the inferred intrinsic reddening of this field in NGC 4725, E(V-I)=0.19, makes it one of the most highly-reddened, encountered by the HST Key Project, to date.