用MUSE观测研究LMC中N44复合体的两个HII区中的光电离气体
A study of photoionized gas in two HII regions of the N44 complex in the LMC using MUSE observations
摘要：
利用甚大望远镜多单元光谱探测器（MUSE）的光学积分场观测资料，结合云光电离模型，研究了大麦云星云N44恒星形成复合体中两个发光HII区的电离结构和物理条件。各种发射线的光谱图揭示了N44 D1的分层电离几何。[O I] 6300 A发射在N44 D1的空间分布表明在H II区的外边界处有部分被覆盖的电离前沿。这些观察结果表明，N44 D1是一个水泡HII区。N44 C中的[O I] 6300 A发射在边界处没有提供明确的电离前沿，而[S II] 6717 A和[O I] 6300 A发射条在内部被发现。首次在这些HII区用光电离模型检验了空间分辨MUSE谱的结果。一个球对称电离有界模型与部分覆盖因子，这是适当的水泡HII地区可以很好地再现观察到的几何形状和大部分的诊断线比在N44 D1。同样，在N44 C中，我们根据观测特征应用了低密度和光学薄模型。模拟结果表明，N44 D1的电离结构和物理条件主要取决于O5 V星的辐射。然而，可能来自超新星或恒星风的局部X射线起着关键作用。在N44 C中，主要贡献来自三颗电离星。
英文摘要：
We use the optical integral field observations with Multi-Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope, together with CLOUDY photoionization models to study ionization structure and physical conditions of two luminous HII regions in N44 star-forming complex of the Large Magellanic Cloud. The spectral maps of various emission lines reveal a stratified ionization geometry in N44 D1. The spatial distribution of [O I] 6300A emission in N44 D1 indicates a partially covered ionization front at the outer boundary of the H II region. These observations reveal that N44 D1 is a Blister HII region. The [O I] 6300A emission in N44 C does not provide a well-defined ionization front at the boundary, while patches of [S II] 6717 A and [O I] 6300A emission bars are found in the interior. The results of spatially resolved MUSE spectra are tested with the photoionization models for the first time in these HII regions. A spherically symmetric ionization-bounded model with a partial covering factor, which is appropriate for a Blister HII region can well reproduce the observed geometry and most of the diagnostic line ratios in N44 D1. Similarly, in N44 C we apply a low density and optically thin model based on the observational signatures. Our modeling results show that the ionization structure and physical conditions of N44 D1 are mainly determined by the radiation from an O5 V star. However, local X-rays, possibly from supernovae or stellar wind, play a key role. In N44 C, the main contribution is from three ionizing stars.
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