标题： 高恒星形成区中的大质量年轻恒星天体 显示英文标题

标题： Massive Young Stellar Objects in high-mass star-forming regions

摘要： K波段的高质量点源光谱显示了20颗年轻的大质量恒星，这些恒星没有光球吸收线，只有发射线。 K波段光谱显示出与周围有星周物质的大质量年轻恒星常见的特征：非常红的颜色（J-K）= 2，CO带头发射，氢发射线（有时双峰），以及FeII和/或MgII发射线。 CO发射来自一个相对密集（~10^10 cm^(-3)）且高温（T ~ 2000-5000 K）的区域，这个区域足够屏蔽来自年轻大质量恒星强烈的紫外辐射场。 CO第一泛音发射的建模表明，CO气体位于距离恒星5天文单位以内。 氢发射是在暴露于紫外辐射的电离介质中产生的。 最好的几何构型是一个致密且中性的星周盘产生CO带头发射，而上层的电离区域则产生氢线。 我们认为，星周盘很可能是吸积通过星周盘残留下来的遗迹。 显示英文摘要

摘要： High-quality K-band spectra of point sources, deeply embedded in massive star-forming regions, have revealed a population of 20 young massive stars showing no photospheric absorption lines, but only emission lines. The K-band spectra exhibit one or more features commonly associated with massive Young Stellar Objects surrounded by circumstellar material: a very red color (J-K) = 2, CO bandhead emission, hydrogen emission lines (sometimes doubly peaked), and FeII and/or MgII emission lines. The CO emission comes from a relatively dense (~10^10 cm^(-3)) and hot (T ~ 2000-5000 K) region, sufficiently shielded from the intense UV radiation field of the young massive star. Modeling of the CO-first overtone emission shows that the CO gas is located within 5 AU of the star. The hydrogen emission is produced in an ionized medium exposed to UV radiation. The best geometrical configuration is a dense and neutral circumstellar disk causing the CO bandhead emission, and an ionized upper layer where the hydrogen lines are produced. We argue that the circumstellar disk is likely a remnant of the accretion via a circumstellar disk.