BPT diagram

来自Shiyin's note
Shen讨论 | 贡献2016年7月15日 (五) 07:25的版本
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  • OIII/Hbeta VS NII/Halpha
不一定4条线都有才能区分,3条加一个upper limit也可以
通常 OIII和Hbeta比较弱,更难探测,主要是一些弱的AGN或者金属丰度比较高的恒星形成星系。
大质量星系容易出现Hbeta强,OIII,低金属丰度容易Halpha强,NII弱;
有一些星系没有巴尔沫线,但是有OIII和NII,(高电离态)
  • 有一个类似的图用[SII]λ6717+6713/Halpha 代替NII/Halpha,成为VO87
该图能区分LINER和AGN,BPT不能
  • OIII/Hbeta 可能不完全能表征AGN
Maragkoudakis et al. (2014) revealed that galaxies with extranuclear star formation can show higher [O III] λ5007/Hβ line ratios, since lower metallicity H II regions in the outer parts of galaxy discs are also capable of producing high-excitation emis- sion lines.
  • 高红移和低红移有一些系统的shift
In order to explain offsets between z ∼ 0 and high- redshift galaxies in diagnostic plots such as the [O iii]/Hβ vs. [N ii]/Hα diagram, it has been proposed that high-redshift galaxies may have higher ionization parameters (Kewley et al. 2015; Cullen et al. 2016), harder ionizing stellar spectra (Steidel et al. 2014), higher density/ISM pressure (Kewley et al. 2013; Sanders et al. 2016), and/or anomalous nitrogen abundance at fixed O/H (Masters 2 Sanders et al. et al. 2014; Shapley et al. 2015; Sanders et al. 2016) compared to z ∼ 0 galaxies. Depending