Gazing Back in Time: James Webb’s Revolutionary Insights into Ancient Galaxies

The large galaxy at the forefront, named LEDA 2046648, is observed as it was over a billion years ago. In contrast, the majority of the other galaxies are viewed at even greater temporal distances. Image courtesy of ESA/Webb, NASA & CSA, A. Martel.

With the James Webb Space Telescope’s deployment, astronomers have achieved an unprecedented level of observation of the universe, approaching the era of the earliest galaxy formation. Throughout most of the universe’s history, a steady relationship has been observed between a galaxy’s star count and its production of heavy elements.

However, recent observations reveal that this stars-to-elements ratio may not apply to the earliest galaxies, possibly due to their ongoing formation process and limited time to generate heavy elements.

The universe, abundant with galaxies composed of stars and gas, becomes a window into the past as we view distant galaxies. The greater the distance of a galaxy, the longer its light takes to reach us, allowing us to trace the evolution of these celestial bodies over the universe’s history.

An “element-stellar mass diagram” illustrates the observed galaxies: the more massive a galaxy, the further to the right it appears; the higher its heavy element content, the higher it is plotted. Present-day galaxies are depicted in gray, while early galaxies observed by Webb are shown in red. These early galaxies exhibit significantly lower heavy element levels compared to later galaxies but align with theoretical predictions, as shown by the blue band. Visualization credits: Kasper Elm Heintz, Peter Laursen.

For the past 12 billion years, galaxies have maintained a balance, exhibiting a fundamental relationship between their star formation and heavy element production. In this context, heavy elements refer to all elements heavier than hydrogen and helium.

This relationship is logical, considering the universe initially comprised only hydrogen and helium, with heavier elements like carbon, oxygen, and iron formed later by stars.

James Webb’s Deeper Gaze

The earliest galaxies are expected to be devoid of heavy elements. However, observing such distant times was previously unfeasible. The redshift effect, which turns light redder the longer it travels, necessitated looking into the infrared spectrum to observe the most distant galaxies. The James Webb Space Telescope’s launch, with its large size and sensitivity, has made this possible.

The telescope has surpassed its own records for observing the most distant galaxies, now seemingly reaching the era of the earliest galaxy formation.

Galactic evolution involves intergalactic gas condensing at the galaxy’s center, igniting star formation, and becoming part of the galaxy’s rotating disk. When stars expire, they return their gas, now enriched with heavy elements, to the galaxy and intergalactic space. Image based on Tumlinson et al. (2017).

A recent study in Nature Astronomy by astronomers from Denmark’s Cosmic Dawn Center at the Niels Bohr Institute and DTU Space in Copenhagen reports the discovery of what appears to be some of the earliest forming galaxies.

Kasper Elm Heintz, the study’s lead and assistant professor at the Cosmic Dawn Center, notes the recent advancements in observing the formation of the first galaxies, made possible by James Webb.

Challenging the Fundamental Relation

The link between a galaxy’s total stellar mass and its heavy element content is nuanced. Adjusting for star formation rate reveals a clear linear relationship: larger galaxies have more heavy elements. However, this relationship is now being questioned by new observations.

The study observed 16 of these early galaxies and found them to have significantly fewer heavy elements than expected, based on their stellar masses and star formation rates. This contrasts with the long-held model of galaxies evolving in equilibrium through most of the universe’s history.

Theoretical Validation

These findings align with theoretical galaxy formation models, which predict similar results. The theory suggests we are observing galaxies in their nascent stages. Gravity gathers gas clumps, initiating star formation.

Had these galaxies evolved undisturbed, their stars would rapidly enrich them with heavy elements. However, the presence of vast amounts of fresh, uncontaminated intergalactic gas challenged this process, flowing into the galaxies faster than the stars could produce heavy elements.

This discovery offers a glimpse into the earliest stages of galaxy formation, which appears more closely linked to intergalactic gas than previously thought.

The study’s authors anticipate that ongoing comprehensive observations by James Webb will soon provide a clearer understanding of how galaxies and the universe’s first structures began forming in the initial billion years post-Big Bang.

Reference: “Dilution of chemical enrichment in galaxies 600 Myr after the Big Bang” by Kasper E. Heintz, Gabriel B. Brammer, Clara Giménez-Arteaga, Victoria B. Strait, Claudia del P. Lagos, Aswin P. Vijayan, Jorryt Matthee, Darach Watson, Charlotte A. Mason, Anne Hutter, Sune Toft, Johan P. U. Fynbo and Pascal A. Oesch, 21 September

Frequently Asked Questions (FAQs) about James Webb Space Telescope

More about James Webb Space Telescope

• James Webb Space Telescope Overview
• Understanding Galaxy Formation
• Insights into Early Universe Galaxies
• Study of Cosmic History with James Webb
• Early Galaxy Formation Research
• The Role of Heavy Elements in Galaxies
• Redshift and Distant Galaxy Observation
• Nature Astronomy: Galaxy Study Publication