High-z galaxies with JWST and local analogues -- it is not only star formation

Understand

I present an analysis of the JWST NIRSpec data of SMACS 0723 released as Early Release Observations.

• As part of this three new redshifts are provided, bringing the total of reliable redshifts to 14.
• I propose a modification to the direct abundance determination method that reduces sensitivity to flux calibration uncertainties by a factor of ~3 and show that the resulting abundances are in good agreement with Bayesian photoionization models of the rest-frame optical spectrum.
• I also show that 6355 is most likely a narrow-line active galactic nucleus (AGN) with $M_* \sim 10^9$ Msun at z=7.66, and argue that 10612 might also have an AGN contribution to its flux through comparison to photoionization models and low-redshift analogues.