New AGN diagnostic diagrams based on the [OIII]λ 4363 auroral line
arxiv(2024)
摘要
The James Webb Space Telescope (JWST) is revolutionizing our understanding of
black holes formation and growth in the early Universe. However, JWST has also
revealed that some of the classical diagnostics, such as the BPT diagrams and
X-ray emission, often fail to identify narrow line TypeII active galactic
nuclei (AGN) at high redshift. Here we present three new rest-frame optical
diagnostic diagrams leveraging the [OIII]λ4363 auroral line, which has
been detected in several JWST spectra. Specifically, we show that high values
of the [OIII]λ4363/Hγ ratio provide a sufficient (but not
necessary) condition to identify the presence of an AGN, both based on
empirical calibrations (using local and high-redshift sources) and a broad
range of photoionization models. These diagnostics are able to separate much of
the AGN population from Star Forming Galaxies (SFGs). This is because the
average energy of AGN's ionizing photons is higher than that of young stars in
SFGs, hence AGN can more efficiently heat the gas, therefore boosting the
[OIII]λ4363 line. We also found independent indications of AGN activity
in some high-redshift sources that were not previously identified as AGN with
the traditional diagnostics diagrams, but that are placed in the AGN region of
the diagnostics presented in this work. We note that, conversely, low values of
[OIII]λ4363/Hγ can be associated either with SFGs or AGN
excitation. We note that the fact that strong auroral lines are often
associated with AGN does not imply that they cannot be used for direct
metallicity measurements (provided that proper ionization corrections are
applied), but it does affect the calibration of strong line metallicity
diagnostics.
更多查看译文
AI 理解论文
溯源树
样例
生成溯源树,研究论文发展脉络
Chat Paper
正在生成论文摘要