paper

Bridging Optical and Far-Infrared Emission-Line Diagrams of Galaxies from Local to the Epoch of Reionization: Characteristic High [O III] 88 /SFR at

arXiv:2207.05236 · doi:10.3847/1538-4357/ac7fed

Abstract

We present photoionization modeling of galaxy populations at , , and to bridge optical and far-infrared (FIR) emission-line diagrams. We collect galaxies with measurements of optical and/or FIR ([O III] 88 and [C II] 158 ) emission line fluxes and plot them on the [O III]--[N II] (BPT) and L([O III]88)/SFR--L([C II]158)/SFR diagrams, where SFR is the star-formation rate and L([O III]88) and L([C II]158) are the FIR line luminosities. We aim to explain the galaxy distributions on the two diagrams with photoionization models that employ three nebular parameters: the ionization parameter , hydrogen density , and gaseous metallicity . Our models successfully reproduce the nebular parameters of local galaxies, and then predict the distributions of the , , and galaxies on the diagrams. The predicted distributions illustrate the redshift evolution on all the diagrams; e.g., [O III] and [O III]88/[C II]158 ratios continuously decrease from to . Specifically, the galaxies exhibit dex higher than low-redshift galaxies at a given and show predicted flat distributions on the BPT diagram at -. We find that some of the galaxies exhibit high L([O III]88)/SFR ratios. To explain these high ratios, our photoionization models require a low stellar-to-gaseous metallicity ratio or bursty/increasing star-formation history at . The James Webb Space Telescope will test the predictions and scenarios for the galaxies proposed by our photoionization modeling.

18 pages + 5 appendix pages, 11 figures, 1 tables. accepted for publication in ApJ

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