A luminous and young galaxy at z=12.33 revealed by a JWST/MIRI detection of H{\alpha} and [OIII]

TL;DR

This paper reports the first detection of Hα and [OIII] lines in a galaxy at z=12.33 using JWST/MIRI, revealing a young, metal-enriched, luminous galaxy with extreme ionizing conditions in the early universe.

Contribution

It provides the first spectroscopic detection of nebular lines in a galaxy at z>10, offering new insights into galaxy properties at cosmic dawn.

Findings

Galaxy GHZ2/GLASS-z12 at z=12.33+/-0.04 is the most distant with direct nebular line detection.

The galaxy shows hard ionizing conditions and rapid metal enrichment.

It is a young (~30 Myr), luminous galaxy with near-solar oxygen abundance.

Abstract

The James Webb Space Telescope (JWST) has discovered a surprising population of bright galaxies in the very early universe (<500 Myrs after the Big Bang) that is hard to explain with conventional galaxy formation models and whose physical properties remain to be fully understood. Insight into their internal physics is best captured through nebular lines but, at these early epochs, the brightest of these spectral features are redshifted into the mid-infrared and remain elusive. Using the JWST Mid-Infrared Instrument, MIRI, here we present the first detection of H{\alpha} and doubly-ionized oxygen ([OIII]5007AA) at z>10. These detections place the bright galaxy GHZ2/GLASS-z12 at z=12.33+/-0.04, making it the most distant astronomical object with direct spectroscopic detection of these lines. These observations provide key insights into the conditions of this primeval, luminous galaxy, which shows hard ionizing conditions rarely seen in the local Universe likely driven by compact and young (~30Myr) burst of star formation. Its oxygen-to-hydrogen abundance is close to a tenth of the solar value, indicating a rapid metal enrichment. This study confirms the unique conditions of this remarkably bright and distant galaxy and the huge potential of mid-IR observations to characterize these objects.