标题： 附近矮星系中的明亮紫外区域与恒星形成特性 显示英文标题

标题： Bright Ultraviolet Regions and Star Formation Characteristics in Nearby Dwarf Galaxies

摘要： 我们比较了11个矮星系（dIm）内部和外部盘中的恒星形成活动，这些星系距离地球不超过3.6百万秒差距。 这些区域通过GALEX近紫外图像识别，并使用紫外、光学和近红外颜色建模以确定质量和年龄。 少数星系在爆发阶段形成了质量为10⁵至10⁶倍太阳质量的复合体，而其他星系在过去50百万年内未形成星团。 最大区域的质量与区域数量之间的关系符合样本大小效应的预期。 我们发现即使在Hα发射之外，区域的质量和年龄也没有径向梯度，尽管区域的亮度密度和数量密度随半径呈指数下降。 Hα在外部区域似乎缺失是因为周围大质量恒星的星云辐射太微弱而无法观测到。 对于有HI数据的5个星系，最外层区域形成的平均气体面密度为1.9-5.9倍太阳质量每平方秒差距。 这些低平均密度表明要么局部气体密度较高，要么亚阈值的恒星形成是可能的。 在对数质量-对数年龄图上区域分布通常沿对数年龄均匀分布。 这种均匀性可能是由于单个区域质量随年龄变化为1/年龄，或者区域破坏概率随年龄变化为1/年龄。 校正消光后的表面亮度与年龄之间的相关性表明前者。 显示英文摘要

摘要： We compare star formation in the inner and outer disks of 11 dwarf Irregular galaxies (dIm) within 3.6 Mpc. The regions are identified on GALEX near-UV images, and modeled with UV, optical, and near-IR colors to determine masses and ages. A few galaxies have made 10^5-10^6 Msun complexes in a starburst phase, while others have not formed clusters in the last 50 Myrs. The maximum region mass correlates with the number of regions as expected from the size-of-sample effect. We find no radial gradients in region masses and ages, even beyond the realm of Halpha emission, although there is an exponential decrease in the luminosity density and number density of the regions with radius. Halpha is apparently lacking in the outer parts only because nebular emission around massive stars is too faint to see. The outermost regions for the 5 galaxies with HI data formed at average gas surface densities of 1.9-5.9 Msun/pc2. These low average densities imply either that local gas densities are high or sub-threshold star formation is possible. The distribution of regions on a log Mass - log age plot is is usually uniform along log age for equal intervals of log Mass. This uniformity results from either an individual region mass that varies as 1/age or a region disruption probability that varies as 1/age. A correlation between fading-corrected surface brightness and age suggests the former.