# Spectroscopic verification of very luminous galaxy candidates in the early universe

**Authors:** Pablo Arrabal Haro, Mark Dickinson, Steven L. Finkelstein, Jeyhan S. Kartaltepe, Callum T. Donnan, Denis Burgarella, Adam Carnall, Fergus Cullen, James S. Dunlop, Vital Fernández, Seiji Fujimoto, Intae Jung, Melanie Krips, Rebecca L. Larson, Casey Papovich, Pablo G. Pérez-González, Ricardo O. Amorín, Micaela B. Bagley, Véronique Buat, Caitlin M. Casey  
**arXiv:** [2303.15431](https://arxiv.org/abs/2303.15431)  
**Date:** 2023-03-27  
**Summary page:** https://www.summarizepaper.com/en/paper/2303.15431v1/

## Key points

- The first 500 million years of cosmic history saw the formation of the first stars and galaxies, which seeded the universe with heavy elements.
- The early galaxies illuminated the transition from the cosmic "dark ages" to the reionization of the intergalactic medium.
- With the commissioning of JWST (James Webb Space Telescope), our observational reach into that epoch has been extended.
- The first JWST science observations have uncovered a surprisingly high abundance of early star-forming galaxies.
- Spectroscopic measurements are required to validate these sources and quantify their space densities, stellar masses, and star formation rates accurately.
- Researchers present results from JWST follow-up spectroscopy of a small sample of galaxies suspected to be amongst the most distant yet observed.
- They confirm redshifts z > 10 for two galaxies, including one of the first bright JWST-discovered candidates with z = 11.4.
- Another galaxy with suggested z ~ 16 instead has z = 4.9, with strong emission lines that mimic expected colors of more distant objects.
- These results reinforce evidence for rapid production of luminous galaxies in the very young Universe while highlighting necessity for spectroscopic verification for remarkable candidates.

## Summary

The first 500 million years of cosmic history saw the formation of the first stars and galaxies, which seeded the universe with heavy elements. These early galaxies illuminated the transition from the cosmic "dark ages" to the reionization of the intergalactic medium. Until recently, this transitional period has been largely inaccessible to direct observation. However, with the commissioning of JWST (James Webb Space Telescope), our observational reach into that epoch has been extended. The first JWST science observations have uncovered a surprisingly high abundance of early star-forming galaxies. Spectroscopic measurements are required to validate these sources and quantify their space densities, stellar masses, and star formation rates accurately. Such measurements provide powerful constraints on galaxy formation models and cosmology. In this study, researchers present results from JWST follow-up spectroscopy of a small sample of galaxies suspected to be amongst the most distant yet observed. They confirm redshifts z > 10 for two galaxies, including one of the first bright JWST-discovered candidates with z = 11.4. They also show that another galaxy with suggested z ~ 16 instead has z = 4.9, with strong emission lines that mimic expected colors of more distant objects. These results reinforce evidence for rapid production of luminous galaxies in the very young Universe while highlighting necessity for spectroscopic verification for remarkable candidates. The research was conducted by an international team comprising scientists from NSF's National Optical-Infrared Astronomy Research Laboratory; University of Connecticut; MMT/Steward Observatory at University of Arizona; University College London; Rochester Institute of Technology; Aix Marseille Univ in France; Universidad de La Serena in Chile; Cosmic Dawn Center (DAWN) in Denmark; Space Telescope Science Institute in Baltimore; IRAM in France; Texas A&M University; Centro de Astrobiología (CAB) in Spain; University of Massachusetts Amherst; Instituto de Astrofísica de Canarias and Universidad de la Laguna in Spain; Université Paris-Cité, LERMA - Observatoire de Paris, PSL in France; NASA Goddard Space Flight Center; and National Astronomical Observatory of Japan.