Searching for Additional Heating: [O II] Emission in the Diffuse Ionized Gas of NGC 891, NGC 4631, and NGC 3079
Searching for Additional Heating: [O II] Emission in the Diffuse Ionized Gas of NGC 891, NGC 4631, and NGC 3079
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寻找额外的加热：NGC 891、NGC 4631 和 NGC 3079 的扩散电离气体中的 [O II] 发射
DOI：
10.1086/322343
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
A. Ferguson
中科院分区：
文献类型：
--
作者：
B. Otte;R. J. Reynolds;J. Gallagher III;A. Ferguson
我们给出了三个边缘星系NGC891、NGC4631和NGC3079盘晕区域的电离气体光谱数据，覆盖的波长范围从[O II]3727？到[S II]6716.4？[O II]发射的包含对扩散电离气体的性质，特别是观测到的谱线强度比空间变化的来源提供了新的约束。我们使用了三种不同的方法来计算沿狭缝的电子温度、丰度和电离分数。在所有三个星系中，[O II]/Hα线比值的增加都要求电子温度或氧丰度的增加。保持氧丰度恒定会产生最合理的温度、丰度和电离分数的结果。由于恒定的氧丰度似乎要求朝向晕的温度升高，我们得出结论，在这三个螺旋星系中，电子温度的梯度对这三个螺旋星系中平面外扩散电离气体的光学线比的观测变化起着重要作用。
We present spectroscopic data of ionized gas in the disk-halo regions of three edge-on galaxies, NGC 891, NGC 4631, and NGC 3079, covering a wavelength range from [O II] 3727 Å to [S II] 6716.4 Å. The inclusion of the [O II] emission provides new constraints on the properties of the diffuse ionized gas, in particular the origin of the observed spatial variations in the line-intensity ratios. We used three different methods to derive electron temperatures, abundances, and ionization fractions along the slit. The increase in the [O II]/Hα line ratio toward the halo in all three galaxies requires an increase in either electron temperature or oxygen abundance. Keeping the oxygen abundance constant yields the most reasonable results for temperature, abundances, and ionization fractions. Since a constant oxygen abundance seems to require an increase in temperature toward the halo, we conclude that gradients in the electron temperature play a significant role in the observed variations in the optical line ratios from extraplanar diffuse ionized gas in these three spiral galaxies.