Interpreting ALMA non-detections of JWST super-early galaxies

Abstract

Recent attempts to detect [OIII] 88$\hat{I}¼$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 $[\mathrm{OIII}]-\mathrm{SFR}$ relation as a result of their low ionization parameter, $U_{\mathrm{ion}}\lesssim 10^{-3}$. Such low $U_{\mathrm{ion}}$ 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 ($\log [{\mathrm{L}}_{[\mathrm{OIII}]}/{\mathrm{L}}_{\odot }]=8.4$, $U_{\mathrm{ion}}\approx 0.1$) could be detected by ALMA in only $2.8$ hrs.

6 pages, 3 figures, Submitted to MNRAS (comments are welcome)