What drives the redshift evolution of strong emission line ratios?
What drives the redshift evolution of strong emission line ratios?
复制标题
是什么驱动强发射线比的红移演化？
DOI：
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
M. Dopita
中科院分区：
文献类型：
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作者：
F. Bian;L. Kewley;B. Groves;M. Dopita
我们研究了在[OIII]/H$上造成高红移星系和低红移星系偏移的物理机制eta$与[NII]/H$alpha$ ``Baldwin，菲利普斯& Terlevich'（BPT）图，使用高红移星系的局部类似物样本。这些高红移的类比星系是从史隆数位巡天计画中挑选出来的。这些高红移模拟星系在BPT图上与紫外选定星系位于相同的区域，为研究BPT图上本星系和高红移星系之间的偏移提供了一个理想的本星系基准。我们比较氮氧比（N/O），电离辐射场的形状，和电离参数之间的高红移类似物和本地参考星系的样本。在高红移类似物中较高的电离参数是驱动BPT偏移从低到高红移的主要物理机制，特别是在高红移处。
ii/ha}。此外，N/O比的提高也起着次要的作用，导致BPT偏移。然而，电离辐射场的形状不太可能导致BPT偏移，因为高红移类似物具有与本地参考星系相似的硬电离辐射场。目前的标准恒星合成模型无法产生这种硬辐射场。恒星自转和双星现象可能有助于解决这个矛盾。
We study the physical mechanisms that cause the offset between low-redshift and high-redshift galaxies on the [OIII]/H$eta$ versus [NII]/H$alpha$ ``Baldwin, Phillips & Terlevich' (BPT) diagram using a sample of local analogues of high-redshift galaxies. These high-redshift analogue galaxies are selected from the Sloan Digital Sky Survey. Located in the same region on the BPT diagram as the ultra-violet selected galaxies at $zsim2$, these high-redshift analogue galaxies provide an ideal local benchmark to study the offset between the local and high-redshift galaxies on the BPT diagram. We compare the nitrogen-to-oxygen ratio (N/O), the shape of the ionising radiation field, and ionisation parameters between the high-redshift analogues and a sample of local reference galaxies. The higher ionisation parameter in the high-redshift analogues is the dominant physical mechanism driving the BPT offset from low- to high-redshift, particularly at high {
ii/ha}. Furthermore, the N/O ratio enhancement also plays a minor role to cause the BPT offset. However, the shape of the ionising radiation field is unlikely to cause the BPT offset because the high-redshift analogues have a similar hard ionising radiation field as local reference galaxies. This hard radiation field cannot be produced by the current standard stellar synthesis models. The stellar rotation and binarity may help solve the discrepancy.