Extragalactic Distance Measurements with Planetary Nebulae_

人们通常会想到用最亮的恒星来确定星系外的距离。50多年前，哈勃首次尝试分辨其他星系中的恒星，以量化宇宙的膨胀，从那时起，利用蓝色和红色超巨星来确定银河系外的距离已经被探索了几次。然而，直到最近人们才认识到，年轻的行星状星云也属于“最亮的恒星”一类，因此有可能用作距离指示器。这些天体的中心恒星几乎和明亮的红色超巨星一样明亮，因此，目前的望远镜和技术允许在2500万秒差距的距离上探测到行星状星云。行星状星云与大多数其他星系外距离指示器相比有几个优势。因为它们不与任何一个恒星群有关，所以它们可以在所有类型的星系中找到，对于探测椭圆星系特别有价值。椭圆星系定义了大星系群和星团的核心。在这项拨款中，对椭圆星系中行星的调查将在距离为2500万秒差距的地方进行。这些测量将增加我们对星系大尺度运动和其他研究的理解。首席研究员是本研究领域公认的专家。

It is common to think of using the brightest stars to determine extragalactic distances. Over 50 years ago Hubble first attempted to resolve stars in other galaxies to quantify the expansion of the universe, and since then, the use of blue and red supergiants for extragalactic distance determinations has been explored several times. However, only recently has it been appreciated that young planetary nebulae also fall into the "brightest stars" category and are therefore potentially useful as distance indicators. The central stars of these objects are almost as luminous as bright red supergiants, and, as a result, present telescopes and current technology allow planetary nebulae to be detected at distances as large as 25 megaparsecs. Planetary nebulae have several advantages over most other extragalactic distance indicators. Because they are not associated with any one stellar population they can be found in all types of galaxies, and are particularly valuable for probing elliptical galaxies. It is elliptical galaxies which define the cores of large groups and clusters. In this grant surveys of planetary in elliptical galaxies will be made out to a distance of 25 megaparsecs. These measurements will add to our understanding of the large scale motions of galaxies and in other studies. The Principal Investigator is a recognized expert in this research area.