标题： 10个矮不规则星系的恒星成分 显示英文标题

标题： The stellar content of 10 dwarf irregular galaxies

摘要： 我们检查了10个矮不规则星系的恒星内容，其中宽波段CCD测光数据已在Hopp & Schulte-Ladbeck (1995)中发表。 我们还为这些星系中的几个提供了Halpha图像。 样本中的星系位于本星系群之外。 然而，它们仍然足够近，可以从地面上解析成单个恒星，但只有最亮的恒星（或星团）被检测到，并且存在严重的拥挤。 所选样本星系是为了远离大质量邻居；其中约一半是（主要是外围）群体成员，另一半位于场域中。 我们讨论了样本星系与其他矮星系的邻近情况。 为了解释单恒星测光并得出关于恒星内容或其他与距离相关的量的结论，关键是要知道星系的准确距离。 由于除了一个以外的所有星系都没有测量主要距离指示器，因此样本星系的距离并不为人所知。 我们尝试通过在B、B-R和R、B-R颜色-星等图中识别最亮超巨星的包络来限制距离，但结果并不十分准确（我们估计距离模数的最小误差为1.36星等）。 尽管如此，这些样本星系能够通过直接的地面成像进行解析，这表明它们足够近，可以作为高空间分辨率仪器观测的良好候选者，例如大型地面望远镜上的自适应光学系统，或哈勃空间望远镜。 显示英文摘要

摘要： We examine the stellar content of 10 dwarf irregular galaxies of which broad-band CCD photometry was published in Hopp & Schulte-Ladbeck (1995). We also present Halpha images for several of these galaxies. The galaxies in the sample are located outside of the Local Group. Yet, they are still close enough to be resolved into single stars from the ground but only the brightest stars (or star clusters) are detected and there is severe crowding. The sample galaxies were selected to be isolated from massive neighbors; about half of them are (mostly peripheral) members of groups, the other half is located in the field. We discuss the vicinity of the sample galaxies to other dwarf galaxies. In order to interpret single-star photometry and draw conclusions about the stellar content or other distance-dependent quantities, it is crucial that accurate distances to the galaxies be known. The distances to the sample galaxies are not well known since all but one have not had a primary distance indicator measured. We make an attempt to constrain the distances by identifying the envelope of the brightest supergiants in B, B-R and R, B-R color-magnitude diagrams, but the results are not very accurate (we estimate the minimal error on the distance modulus is 1.36 mag). Nevertheless, the fact that the sample galaxies are resolved with direct ground-based imaging indicates that they are sufficiently nearby to represent good candidates for observations with instruments that provide high spatial resolution, e.g., adaptive optics systems on large ground-based telescopes, or the Hubble Space Telescope. ...