NGC 1222（Mkn 603）的异常红外光谱
The Extraordinary Infrared Spectrum of NGC 1222 (Mkn 603)
摘要：
星暴星系的红外光谱主要由[NeII]和[SIII]的低激发谱线所控制，从这些光谱推断的恒星星族似乎缺乏大于35 Msun的恒星。到目前为止，唯一的例外是低金属量的矮星系。本文分析了星暴星系NGC 1222（Mkn 603）在斯皮策望远镜上的中红外光谱。NGC 1222是一个大型球状星系，其星暴核心是一个紧凑的射电和红外源，其红外辐射主要由[NeIII]线控制。这是我们所知的第一次太阳或近太阳金属丰度的恒星爆发，它由高激发线主导，可能是高质量恒星的宿主。我们模拟的排放与几个不同的假设的空间分布的高，低激发线，并发现在这个星系的上限质量截止为40-100 Msun。
英文摘要：
The infrared spectra of starburst galaxies are dominated by the low-excitation lines of [NeII] and [SIII], and the stellar populations deduced from these spectra appear to lack stars larger than about 35 Msun. The only exceptions to this result until now were low metallicity dwarf galaxies. We report our analysis of the mid-infrared spectra obtained with IRS on Spitzer of the starburst galaxy NGC 1222 (Mkn 603). NGC 1222 is a large spheroidal galaxy with a starburst nucleus that is a compact radio and infrared source, and its infrared emission is dominated by the [NeIII] line. This is the first starburst of solar or near-solar metallicity, known to us, which is dominated by the high-excitation lines and which is a likely host of high mass stars. We model the emission with several different assumptions as to the spatial distibution of the high- and low-excitation lines and find that the upper mass cutoff in this galaxy is 40-100 Msun.
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