First Insights into the ISM at 𝑧 > 8 with JWST: Possible Physical Implications of a High [O III]𝜆4363/[O III]𝜆5007
https://arxiv.org/pdf/2207.13693.pdf
Non-thermal processes may become important as we probe deeper into the Epoch of Reionization thanks to JWST.
We found that S06355 at 𝑧 = 7.67 and S10612 at 𝑧 = 7.66 are similar to local Green Peas and Blueberries. In contrast, S04590 at 𝑧 = 8.50 appears to be significantly different from the other two galaxies, most resembling extremely low-metallicity systems in the local Universe. Perhaps the most striking spectral feature in S04590 is the curiously high [O III] 𝜆4363/[O III] 𝜆5007 ratio (RO3) of 0.047 (or 0.059 when dust-corrected), implying either extremely high electron temperatures . High-mass X-ray binaries or a high cosmic ray background in addition to a young, low-metallicity stellar population can provide the additional heating necessary to explain the observed high RO3.