Confirming very bright galaxies in the early universe, while also disproving the identification of what would have been the most distant galaxy ever found

Mollie Radzinski

Kartaltepe and Larson co-authored a paper, “Confirmation and refutation of very luminous galaxies in the early Universe,” published in Nature confirming very bright galaxies in the early universe, while also disproving the identification of what would have been the most distant galaxy ever found.

The CEERS team focused on Maisie’s Galaxy, which was theorized to have a redshift of z ≈ 11.5, while a team in Scotland researched a nearby galaxy that they believed could have a redshift of z ≈ 16, far larger than any ever found before.

"Spectra are how you really confirm what a galaxy's redshift is," explained Kartaltepe. "For these two galaxies, the answer was very clear -- the spectra look completely different. We confirmed that Maisie's Galaxy is at the high redshift we thought it was."

The group also found that because of a coincidence that mimicked the colors of a high redshift galaxy, the other galaxy is not at a redshift of z ≈ 16, but at a redshift of z ≈ 4.9. Both the initial and follow-up data from JWST turned the theories into discoveries.

Link to the research article (paywalled)

Here we present JWST spectroscopy that confirms redshifts for two very luminous galaxies with z > 11, and also demonstrates that another candidate with suggested z ≈ 16 instead has z = 4.9, with an unusual combination of nebular line emission and dust reddening that mimics the colours expected for much more distant objects. These results reinforce evidence for the early, rapid formation of remarkably luminous galaxies while also highlighting the necessity of spectroscopic verification.