论文标题
是什么推动了强发线比的红移演变？
What Drives the Redshift Evolution of Strong Emission Line Ratios?
论文作者
论文摘要
我们研究了在[OIII]/H $β$上的低红移和高红移星系中的偏移的物理机制，vers [nii]/h $α$```baldwin''baldwin，Phillips＆terlevich'（bpt）（bpt）图（bpt）图，该图使用了当地的高速度造型星座的当地类似物的样品。这些高红移模拟星系是从斯隆数字天空调查中选择的。这些高红移模拟星系位于BPT图上的同一区域，与$ z \ sim2 $处的超紫罗莱夹选定的星系相同，为研究BPT图上局部和高红色速度星系之间的偏移提供了理想的局部基准。我们比较了氮与氧比（N/O），电离辐射场的形状以及高红移类似物和局部参考星系样本之间的电离参数。高红移类似物中较高的电离参数是使BPT偏移从低 - 红移偏移的主要物理机制，尤其是在高{\ nii/\ ha}下。此外，N/O比增强也起着较小的作用，导致BPT偏移。但是，由于高偏移类似物具有与局部参考星系相似的硬电离辐射场，因此电离辐射场的形状不太可能引起BPT偏移。当前标准恒星合成模型无法产生这种硬辐射场。恒星旋转和二进制性可能有助于解决差异。
We study the physical mechanisms that cause the offset between low-redshift and high-redshift galaxies on the [OIII]/H$β$ versus [NII]/H$α$ ``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 $z\sim2$, 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 {\nii/\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.
