Diffuse Ionized Gas in Three Sculptor Group Galaxies
Diffuse Ionized Gas in Three Sculptor Group Galaxies
复制标题
三个玉夫座星系中的弥散电离气体
DOI：
10.1086/118111
复制
发表时间：
1996
期刊：
影响因子：
--
通讯作者：
B. Greenawalt
中科院分区：
文献类型：
--
作者：
C. Hoopes;R. Walterbos;B. Greenawalt
本文对玉夫座星系群中的三个星系NGC 55、NGC 253和NGC 300的弥漫电离气体（DIG）进行了研究。该研究基于H-α +[NII]（6548+ 6583 A）和[SII]（6717+ 6731 A）的窄带图像。我们发现DIG贡献了这些星系中总H-α光度的33%至58%，或者在校正散射光后为30%至54%。我们发现NGC 300比我们样本中的其他星系有更高的分数DIG光度，但还不清楚这是一个显着的差异还是其他星系的高倾角的影响。漫发射在圆盘的光学范围内取平均值，其正面发射测量值为5至10 pc cm^{-6}。DIG集中在HII区域附近，尽管在距离HII区域很远的地方可以看到显著的排放，高达0.5至1千秒差距。[SII]/（H-alpha+[NII]）比率在DIG中增强，通常在0.3到0.5之间，而在这些星系中的HII区域为0.2。这些性质与银河系和附近其他螺旋星系中DIG的测量结果相似。谱线比、大尺度分布和能量需求表明，光电离是主要的电离机制。
We present a study of the diffuse ionized gas (DIG) in three Sculptor group galaxies: NGC 55, NGC 253, and NGC 300. The study is based on narrow band imagery in H-alpha+[NII](6548+6583A) and [SII] (6717+6731A). We find that DIG contributes 33 to 58% of the total H-alpha luminosity in these galaxies, or 30 to 54% after correcting for scattered light. We find that NGC 300 has a higher fractional DIG luminosity than the other galaxies in our sample, but it is not clear whether this is a significant difference or an effect of the high inclination of the other galaxies. The diffuse emission, averaged over the optical extent of the disk, has a face-on emission measure of 5 to 10 pc cm^{-6}. The DIG is concentrated near HII regions, although significant emission is seen at large distances from HII regions, up to 0.5 to 1 kpc. The [SII]/(H-alpha+[NII]) ratio is enhanced in the DIG, typically around 0.3 to 0.5, compared to 0.2 for the HII regions in these galaxies. These properties are similar to those measured for the DIG in the Milky Way and in other nearby spirals. The line ratios, large-scale distribution, and energy requirement suggest that photoionization is the dominant ionization mechanism.