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arXiv 1504.04013astro-ph.GA
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在棒星系中发现kpc尺度线发射,与AGN或恒星形成无关

Discovery of kpc-scale line emission in barred galaxies, not linked to AGN or star formation

Phil A. James, Susan M. Percival

摘要:

我们提出了一个分析的光学线发射附近的棒星系,特别是看径向范围所占据的酒吧。在许多情况下,这一地区的特点是我们所谓的“恒星形成沙漠”,与一个显着的赤字HII地区的光学窄带H-α成像。在这里,我们提出的长缝光谱揭示,这些地区确实有线发射,但它是低水平的,空间平滑,几乎无处不在。H-α和光谱相邻的[NII]线在该地区的相对强度是完全不一致的,从那些与恒星形成区,并更接近匹配的预期'LINER'地区。我们从这些扩展的,kpc尺度的区域量化的总线发射,并确定虚假的贡献,它会使这些星系的恒星形成率,如果解释为正常的H-α发射。我们同意以前的研究,链接到旧的恒星星族,如后渐近巨星分支星,这种LINER发射,并提出这些强禁止早期型螺旋作为进一步测试这种发射的主要位置。

英文摘要:

We present an analysis of the optical line emission from nearby barred galaxies, and in particular look at the radial range occupied by the bar. In many cases this region is marked by what we term a 'star formation desert', with a marked deficit of HII regions in optical narrow-band H-alpha imaging. Here we present long-slit spectroscopy revealing that such regions do have line emission, but that it is low-level, spatially smooth and almost ubiquitous. The relative strengths of the H-alpha and the spectrally adjacent [NII] lines in the regions are completely discrepant from those associated with star formation regions, and more closely match expectations for 'LINER' regions. We quantify the total line emission from these extended, kpc-scale regions, and determine the spurious contribution it would make to the determined star formation rate of these galaxies if interpreted as normal H-alpha emission. We concur with previous studies that link this LINER emission to old stellar populations, e.g. post-asymptotic giant branch stars, and propose these strongly-barred early-type spirals as a prime location for further tests of such emission.

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