标题： 超紧致HII区G45.12+0.13的近红外光谱学研究 显示英文标题

标题： Near Infrared Spectroscopy of the Ultracompact HII region G45.12+0.13

摘要： 我们展示了超紧致HII区域G45.12+0.13的完整低分辨率IJHK光谱。 从观测到的HI线强度，我们推导出一个近红外消光定律，比平均值稍陡。 用这个消光定律校正后，我们发现HeI、Fe+、Fe++、S+和S++的观测线比值与可用的原子数据有很好的一致性。 我们的数据显示，G45.12+0.13核心内的密度至少必须达到10^4/cm^3。 这与已知的HII区域的无线电结构一致，并且与以前使用中红外和远红外线的工作有很大不同。 在HeI 2 3P-2 3S跃迁中也一定存在相当大的不透明度，我们展示了其他HeI线的观测强度如何与此一致。 通过对光致电离结构的建模，如果最热的恒星具有 Teff < 42000K，我们发现与大多数观测数据有很好的一致性。 考虑氦离子化状态对这个值设定了一个下限，因此我们还可以限制Teff > 38000K。 一些观测和模型线比值之间仍然存在差异，但最明显的往往是中红外观测。 显示英文摘要

摘要： We present complete, low resolution IJHK spectroscopy of the ultracompact HII region, G45.12+0.13. From the observed HI line strengths, we derive a near infrared extinction law that is slightly steeper than the average. After correction with this extinction law, we find good agreement between the observed line ratios of HeI, Fe+, Fe++, S+ and S++ and the available atomic data. Our data show that the density within the core of G45.12+0.13 must be at least 10^4/cm^3. This is consistent with the known radio structure of the HII region and in considerable disagreement with previous work using mid and far infrared lines. There must also be considerable opacity in the HeI 2 3P-2 3S transition, and we show how the observed strengths of the other HeI lines are consistent with this. From modelling the photoionisation structure, we find good agreement with most of the observed data if the hottest star present has Teff < 42000K. Consideration of the helium ionisation state places a lower limit on this value so that we can also constrain Teff > 38000K. Discrepancies still exist between some of the observed and model line ratios, but the most obvious tend to be the mid-IR observations.