Interpreting ALMA non-detections of JWST super-early galaxies

TL;DR

This paper explains why JWST super-early galaxies are often undetected in [OIII] emission, attributing it to their low ionization parameters and early evolutionary stage, with some luminous cases detectable by ALMA.

Contribution

It demonstrates through simulations that low ionization parameters cause faint [OIII] emission in early galaxies, providing insights into their detectability with ALMA.

Findings

Most super-early galaxies have low ionization parameters, making [OIII] emission faint.

The most luminous galaxy in the sample could be detected by ALMA in under 3 hours.

Low ionization parameters are linked to early galaxy assembly and embedded star formation.

Abstract

Recent attempts to detect [OIII] 88$\mu$m emission from super-early ($z>10$) galaxy candidates observed by JWST have been unsuccessful. By using zoom-in simulations, we show that these galaxies are faint, and mostly fall below the local metal-poor $\rm [OIII]-SFR$ relation as a result of their low ionization parameter, $U_{\rm ion}\lesssim 10^{-3}$. Such low $U_{\rm ion}$ values are found in galaxies that are in an early assembly stage, and whose stars are still embedded in high-density natal clouds. However, the most luminous galaxy in our sample ($\rm{log}[L_{\rm{[OIII]}}/L_\odot] = 8.4$, $U_{\rm ion} \approx 0.1$) could be detected by ALMA in only $2.8$ hrs.