船底座星云中的小球状体
The tiny globulettes in the Carina Nebula
摘要：
在新生星团周围的许多H II区都有大量的小分子云。在光学图像中，这些所谓的小球状体在明亮的星云背景下呈现出黑色的轮廓。我们已经在船底座星云中定位了近300个小球状体。这些物体看起来像是约束良好的密集团块，通常没有较薄的封套、明亮的边缘和尾部。有些小球状体稍微拉长，主轴朝向复合体中年轻星团的方向。许多物体是相当孤立的，并且与该区域的其他分子结构的投影距离>1.5 pc。没有一个小球状体与该地区已识别的主序前天体的位置相吻合。这些天体系统地比其他H II区的天体小得多，质量小得多，密度大得多。几乎所有的小球状体都有行星的质量，而且大多数的质量都小于木星的质量。有几个天体的平均数密度超过了10^5 cm^-3。我们发现了密度和半径（质量）之间的统计关系，即最小的物体也是密度。小globulettes在船底座的人口似乎代表了一个更先进的进化状态比其他H II地区的调查。这些物体在强烈的辐射场中会受到侵蚀，这将导致任何较薄的外壳被移除，并揭开随着时间的推移变得更加紧凑的核心。我们讨论的可能性，核心可能会变得引力不稳定，在这种情况下，自由浮动的行星质量的物体可以形成。
英文摘要：
Small molecular cloudlets are abundant in many H II regions surrounding newborn stellar clusters. In optical images these so-called globulettes appear as dark silhouettes against the bright nebular background. We have located close to 300 globulettes in the Carina Nebula. The objects appear as well-confined dense clumps and, as a rule, lack thinner envelopes, bright rims, and tails. Some globulettes are slightly elongated with their major axes oriented in the direction of young clusters in the complex. Many objects are quite isolated and reside at projected distances >1.5 pc from other molecular structures in the region. No globulette coincides in position with recognized pre-main-sequence objects in the area. The objects are systematically much smaller, less massive, and much denser than those surveyed in other H II regions. Practically all globulettes are of planetary mass, and most have masses less than one Jupiter mass. The average number densities exceed 10^5 cm^-3 in several objects. We have found a statistical relation between density and radius (mass) in the sense that the smallest objects are also the densest. The population of small globulettes in Carina appears to represent a more advanced evolutionary state than those investigated in other H II regions. The objects are subject to erosion in the intense radiation field, which would lead to a removal of any thinner envelope and an unveiling of the core, which becomes more compact with time. We discuss the possibility that the core may become gravitationally unstable, in which case free-floating planetary mass objects can form.
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