标题： 哈勃空间望远镜对大麦云中场星族的远紫外成像 显示英文标题

标题： Far-Ultraviolet Imaging of the Field Star Population in the Large Magellanic Cloud with HST

摘要： 我们对最深的纯紫外观测进行了分析，这是迄今为止进行的角分辨率最高的观测，一组12次曝光使用HST WFPC2和F160BW滤光片，在并行观测模式下获得，覆盖了LMC中位于棒状结构北侧以及LMC的“一般场”区域的$\sim$12平方角分。 341个独立测量值涉及198个天体，代表累积曝光时间$\geq 2 10^4$秒，并揭示了亮度低至m$_{UV}\simeq$22星等的恒星。 观测结果表明，LMC的紫外辐射中有$\sim 2/3$是由我们HST探测到的场中的紫外恒星发出的，即不在星团或星协中。 我们在ROE/NRL光度目录中为$\sim 1/3$的天体找到了光学对应物。 这些结果用于讨论这些紫外源的性质，估计LMC的弥漫紫外辐射作为矮星系的原型，并评估场星对LMC中球状星团和开放星团紫外观测的污染。 我们发现，LMC一般场中紫外恒星的投影密度比太阳附近银河系盘面的高几倍。 将我们的数据与UIT的观测相结合，使我们能够从$m_{UV}=8$到18星等定义恒星的紫外光度函数，并确认LMC的场区域在过去1 Gyr内以稳定的速率形成恒星，其初始质量函数接近Salpeter定律。 显示英文摘要

摘要： We present an analysis of the deepest pure-UV observations with the highest angular resolution ever performed, a set of 12 exposures with the HST WFPC2 and F160BW filter obtained in parallel observing mode, which cover $\sim$12 square arcminutes in the LMC, North of the bar and in the ``general field'' regime of the LMC. The 341 independent measurements of 198 objects represent an accumulated exposure of $\geq 2 10^4$ sec and reveal stars as faint as m$_{UV}\simeq$22 mag. The observations show that $\sim 2/3$ of the UV emission from the LMC is emitted by our HST-detected UV stars in the field, i.e., not in clusters or associations. We identified optical counterparts in the ROE/NRL photometric catalog for $\sim 1/3$ of the objects. The results are used to discuss the nature of these UV sources, to estimate the diffuse UV emission from the LMC as a prototype of dwarf galaxies, and to evaluate the contamination by field stars of UV observations of globular and open clusters in the LMC. We find that the projected density of UV stars in the general field of the LMC is a few times higher than in the Galactic disk close to the Sun. Combining our data with observations by UIT allows us to define the stellar UV luminosity function from $m_{UV}=8$ to 18 mag, and to confirm that the field regions in the LMC have been forming stars at a steady rate during the last 1 Gyr, with an IMF close to the Salpeter law.