ISM properties in low-metallicity environments I. mid-infrared spectra of dwarf galaxies
ISM properties in low-metallicity environments I. mid-infrared spectra of dwarf galaxies
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DOI：
10.1051/0004-6361:20053890
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发表时间：
2005-10
期刊：
影响因子：
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通讯作者：
S. Madden;F. Galliano;A. Jones;M. Sauvage
中科院分区：
文献类型：
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作者：
S. Madden;F. Galliano;A. Jones;M. Sauvage
我们提出了新的ISOCAM中红外光谱的三个恒星爆发附近的矮星系，NGC 1569，IIZw 40，NGC 1140和30 Dor地区的LMC和探索的ISM在低金属环境中的属性，还使用额外的来源从文献中。我们分析了ISM探测的中红外观测的各个组成部分，并将它们与其他银河系和河外天体进行比较。低金属丰度星暴源的MIR光谱主要由[NeIII]和[SIV]线以及急剧上升的尘埃连续体组成。PAH带一般都很微弱，无论是局部还是整个星系的平均值，与尘埃星爆星系形成鲜明对比，那里的PAH特征非常明显，甚至在全球范围内占主导地位。的硬度建模的星际辐射场的矮星系的PAH带发射的存在变得不那么明显。在整个星系中，[NeIII]/[NeII]的平均比值非常高，通常大于10。因此，硬辐射场是明显的和普遍的。我们发现一个显着的相关性之间的多环芳烃/VSGs和[NeIII]/[NeII]的比率为广泛的对象，包括低金属丰度星系以及银河系HII地区和其他富含金属的星系。这种效果是一致的硬度的星际辐射场发挥了重要作用，多环芳烃在低金属ISM的破坏。我们看到了多环芳烃/挥发性葡萄糖和金属含量之间的相关性，Engelbracht等人（2005年）在一项更大的调查中也发现了这一点。金属丰度和辐射场的共同作用对多环芳烃在低金属丰度体系中的行为有重要影响。
We present new ISOCAM mid-infrared spectra of three starbursting nearby dwarf galaxies, NGC1569, IIZw40, NGC1140 and the 30Dor region of the LMC and explore the properties of the ISM in low-metallicity environments, also using additional sources from the literature. We analyse the various components of the ISM probed by the mid-infrared observations and compare them with other Galactic and extragalactic objects. The MIR spectra of the low-metallicity starburst sources are dominated by the [NeIII] and [SIV] lines, as well as a steeply rising dust continuum. PAH bands are generaly faint, both locally and averaged over the full galaxy, in stark contrast to dustier starburst galaxies, where the PAH features are very prominant and even dominate on global scales. The hardness of the modeled interstellar radiation fields for the dwarf galaxies increases as the presence of PAH band emission becomes less pronounced. The [NeIII]/[NeII] ratios averaged over the full galaxy are strikingly high, often >10. Thus, the hard radiation fields are pronounced and pervasive. We find a prominent correlation between the PAHs/VSGs and the [NeIII]/[NeII] ratios for a wide range of objects, including the low metallicity galaxies as well as Galactic HII regions and other metal-rich galaxies. This effect is consistent with the hardness of the interstellar radiation field playing a major role in the destruction of PAHs in the low metallicity ISM. We see a PAHs/VSGs and metallicity correlation, also found by Engelbracht et al. (2005) for a larger survey. Combined effects of metallicity and radiation field seem to be playing important roles in the observed behavior of PAHs in the low metallicity systems.