James Webb’s “extra massive” galaxies may be much larger than that


James Webb "very huge" Galaxies may be more massive

This image of galaxy cluster SMACS 0723 and its surroundings was the first image released from the James Webb Space Telescope in July 2023. Each about 19,000 light-years across, it shows galaxies seen about 13 billion years ago in time. Careful analysis of these galaxies reveals that if we cannot resolve a galaxy, we may severely underestimate the total mass of its stars. Credit: NASA, ESA, CSA, and STScI / Giménez-Arteaga et al. (2023), Peter Laursen (Cosmic Dawn Center)

The first results from the James Webb Space Telescope pointed to galaxies so early and so massive that they are in tension with our understanding of structure formation in the universe. Various explanations have been proposed that may relieve this tension. But now a new study from the Cosmic Dawn Center points to an effect that had not been studied before at such early ages, suggesting that the galaxies may be even more massive.

If you’ve been following the first results from the James Webb Space Telescope, you’ve probably heard about the main problem with the first galaxies’ observations: They’re just too big.

A few days after the first images were released, and repeatedly over the coming months, new reports emerged of ever more distant galaxies. Worryingly, many of the galaxies appeared “too huge”.

From the currently accepted conformance model of the structure f The evolution of the universethe so-called ΛCDM model, they simply should not have had time to form so many stars.

Although ΛCDM is not an indestructible holy grail, there are several reasons why we should wait to claim a model transfer: The measured epochs in which we see galaxies can be underestimated.

Their stellar masses can be overestimated. Or maybe we just got lucky and somehow discovered the most massive galaxies of that time.

closer look

But now Clara Jimenez Artega, Ph.D. student at the Cosmic Dawn Center, suggests an effect that can increase stress.

Basically, a galaxy’s stellar mass is estimated by measuring the amount of light emitted by the galaxy, and calculating the number of stars needed to emit that amount. The usual approach is to consider the combined light from the entire galaxy.

However, taking a closer look at a sample of five galaxies, observed with James Webb, Giménez Arteaga found that if a galaxy is not viewed as one large cluster of stars, but as an entity consisting of multiple masses, a different picture emerges.

“We used the standard procedure for calculating stellar masses from images taken by James Webb, but on a pixel-by-pixel basis rather than looking at the entire galaxy,” says Giménez Arteaga.

“In principle, one might expect the results to be the same: adding the light from all the pixels and finding the total stellar mass, versus calculating the mass of each pixel and adding all the individual stellar masses. But it’s not.”

In fact, the now inferred stellar masses turned out to be ten times larger.

The figure below shows the five galaxies with their stellar masses determined by the two methods. If the two different approaches agree, all galaxies will lie along the oblique line labeled “the same”. But they all lie above this line.

James Webb "very huge" Galaxies may be more massive

The five galaxies are placed in a graph showing both the stellar mass inferred by the “usual” method (blue numbers) and the Clara Jimenez-Arteaga method per pixel (red numbers). In all cases, the blocks found using the pixel method are one pixel larger. Credit: Giménez-Arteaga et al. (2023), Peter Laursen (Cosmic Dawn Center)


So why are stellar masses getting so much bigger?

Giménez Arteaga explains, “Stellar clusters are a mixture of small and faint stars on the one hand, and luminosity, huge stars On the other side. If we just look at the common light, then bright stars He will tend to completely outshine the fainter stars, leaving them unnoticed. Our analysis shows that bright star-forming clumps may dominate the overall light, but the bulk of the mass is found in smaller stars.

Star mass is one of the main characteristics used to describe a galaxy, and the Giménez-Arteaga result highlights the importance of being able to resolve galaxies.

But for the most remote and vulnerable, this is not always possible. The effect has been studied before, but only in later periods of the history of the universe.

So the next step is to look for signatures that don’t require high resolution and that correlate with the “real” stellar mass.

“Other studies in later periods have also found this discrepancy. If we can identify and quantify how common and intense the influence was in earlier eras, we will be closer to deducing the strength of stellar audiences from distant galaxies, which is one of the major current challenges of the study galaxies At the beginning of the universe “, concludes Clara Jimenez Arteaga.

The study has just been published in Astrophysical Journal.

ΛCDM model

“ΛCDM” – pronounced “Lambda-CDM” – is the nickname given to our best model for describing the structure and evolution of the universe. The model is based on one of the most well-tested theories in physics, the general theory of relativity, which describes how matter affects space, and how space affects matter.

In this model, the universe is assumed to consist primarily of an unknown substance known as dark energydenoted by the Greek letter Λ, and cold dark matter (CDM), where “cold” means not moving very fast.

ΛCDM has been very successful in describing and predicting many phenomena. But we still don’t know what dark matter and energy are, and we know that general relativity, while successful, is not a complete theory. We therefore expect that ΛCDM will eventually be extended or replaced by a better theory.

more information:
Clara Giménez-Arteaga et al, Spatially resolved properties of galaxies at 5 Astrophysical Journal (2023). DOI: 10.3847/1538-4357/acc5ea

Introduction of
Niels Bohr Institute

the quote: James Webb’s ‘Extremely Massive’ Galaxies May Be Even More Massive (2023, May 17) Retrieved May 18, 2023 from https://phys.org/news/2023-05-james-webb-massive-galaxies.html

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