Astronomy & Space

New evidence on the nature of stuff from early cosmic galaxies

The discovery of galaxies from 13 billion years ago by the James Webb Space Telescope (JWST) and brand-new, cutting-edge numerical simulations of the first galaxies have provided astronomers in Italy with new insight into the nature of matter. The research adds yet another element to our understanding of the nature of matter in the universe.

While the widely accepted paradigm of structure formation is based on non-relativistic matter that interacts only gravitationally, or “cold” dark matter, alternative hypotheses proposed to address small-scale issues with the standard scenario rely on the idea that dark matter is composed of warm particles that have a small, non-negligible thermal velocity, or “warm” dark matter.

Dr. Umberto Maio, staff researcher at the Italian National Institute of Astrophysics (INAF), the Astronomical Observatory of Trieste, and the paper describing the discovery that was just published in Astronomy and Astrophysics state that “we found that the recent JWST galaxy detections in the first fraction of a billion years after the Big Bang are precious probes of the nature of matter.”.

“We discovered that recent JWST galaxy detections in the first billion years after the Big Bang are valuable probes of the nature of matter,”

 Dr. Umberto Maio, staff researcher at the Italian National Institute of Astrophysics (INAF),

According to the research, the primary component of matter in the universe, dark matter, is composed of particles with masses greater than 2 keV that are either “cold” or only slightly “warm.” The study excludes dark-matter models with particle masses that are equal to or lighter than such a limit.

While earlier studies had disregarded the possibility of distinguishing the nature of the matter by using data from more recent epochs, the new study’s foundation required data from much earlier times and ad hoc numerical simulations in order to provide details about the statistical trends of primordial galaxies and break the degeneracies of the models.

What we did, according to Dr. Dodot Maio, was use our brand-new, highly advanced numerical implementation of early galaxy formation to interpret the most recent JWST data. The visible characteristics of the universe’s structures depend on the mass of the dark-matter particle during the time when the first stars and galaxies are forming, as we observed.

According to the study, there is evidence that the rates of cosmological star formation, ultraviolet luminosities, and molecular abundances differ in various dark-matter theories. These variations can be compared to the most recent JWST data, which was the first to reach the “ancient” universe.

The INAF-Astronomical Observatory of Trieste and the International School for Advanced Studies of Trieste, Italy, worked together on the study. The study was founded on the exceptional observations of galaxies in the first half billion years discovered by the JWST and promptly released in late 2022, according to Prof. Matteo Viel, a co-author of the study from the International School for Advanced Studies in Trieste. This is a significant application of scientific data to constrain the characteristics of dark matter at such early epochs. The most distant galaxies in the universe have been observed by JWST, and their characteristics provide us with clear details about their components.”.

JWST, an international partnership between the Canadian Space Agency (CSA), the European Space Agency (ESA), and the American National Aeronautics and Space Administration (NASA), made it possible to accomplish this significant feat. The study demonstrates how two observables, galaxy luminosity function and galaxy correlation function at small scales of faint objects, particularly when used in combination, are promising tools for differentiating between various dark-matter models. The study’s conclusions are also consistent with the characteristics of the “cosmic web,” an intergalactic medium, at more recent epochs.

The scientists write, “Further hints may come from early stellar-mass statistics and galaxy emission of carbon monoxide in the future, when more data for small, dim, young sources will be available.”. The discovery of these young galaxies shows that these structures can develop in as little as a fraction of a billion years, or what we would refer to as the blink of an eye in cosmological terms. So, in the near future, it will be possible to detect more and more early star-forming galaxies, which will open the door to a better understanding of the origin of matter.

More information: Umberto Maio et al, JWST high-redshift galaxy constraints on warm and cold dark matter models, Astronomy & Astrophysics (2023). DOI: 10.1051/0004-6361/202345851

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