ALMA observations of super-early galaxies: attenuation-free model predictions

The abundance and blue color of super-early (redshift $z>10$), luminous galaxies discovered by JWST can be explained if radiation-driven outflows have ejected their dust on kpc-scales. To test this hypothesis, we predict the ALMA detectability of such extended dust component. Given the observed properties of the galaxy, its observed continuum flux at 88 $\mu$m, $F_{88}$, depends on the dust-to-stellar mass ratio, $\xi_d$, and extent of the dust distribution, $r_d$. Once applied to the most distant galaxy known, GS-z14-0 at $z=14.32$, the fiducial model ($\xi_d = 1/529$) predicts $F_{88}^{\rm fid} = 14.9\, \mu$Jy, and a dust extent $r_d=1.4$ kpc. If the galaxy is very dust-rich ($\xi_d =1/40$), $F_{88}^{\rm max} = 40.1\, \mu$Jy. These values are smaller ($F_{88}^{\rm fid} = 9.5\, \mu$Jy) if the dust is predominantly made of large grains as those formed in SN ejecta. Forthcoming ALMA observations might come very close to constraining the fiducial predictions of the outflow-based attenuation-free model. Other super-early galaxies are predicted to be fainter at 88 $\mu$m, mostly because of their lower SFR compared to GS-z14-0, with fiducial fluxes in the range $2-5.2\ \mu$Jy.