ZF-UDS-7329: A relic galaxy in the early Universe

TL;DR

This paper uses JWST data to analyze a massive galaxy in the early Universe, demonstrating that high-redshift observations can resolve formation timescales and identify relic galaxies like ZF-UDS-7329, similar to local relics.

Contribution

It introduces a method to match chemical and star formation timescales at high redshift using JWST data, identifying ZF-UDS-7329 as a relic galaxy candidate.

Findings

ZF-UDS-7329 is a relic galaxy in the early Universe.

High redshift observations improve time resolution of galaxy formation.

ZF-UDS-7329 resembles local relic galaxy NGC 1277.

Abstract

The formation time scales of quiescent galaxies can be estimated in two different ways: by their star formation history and by their chemistry. Previously, the methods yielded conflicting results, especially when considering $\alpha$-enhanced objects. This is primarily due to the time resolution limitations of very old stellar populations, which prevent accurately constraining their star formation histories. We analysed the JWST observations of the extremely massive galaxy ZF-UDS-7329 at z$\sim$3.2 and show that the higher time resolution necessary to match the chemical formation time scales using stellar population synthesis can be achieved by studying galaxies at high redshift. We compare the massive galaxy to the well-known relic galaxy NGC~1277, arguing that ZF-UDS-7329 is an early Universe example of the cores of present-day massive elliptical galaxies or, if left untouched, a relic galaxy.