New evidence for the nature of matter in the ancient universe

Distribution of primordial matter in cosmological models with hot dark matter (WDM, left) and cold dark matter (CDM, right).

Distribution of primordial matter in cosmological models with hot dark matter (WDM, left) and cold dark matter (CDM, right). -INAF


Observations of James Webb Space Telescope (JWST) and state-of-the-art numerical simulations of the first galaxies have shed new light on the nature of matter.

Although the commonly accepted paradigm of structure formation is based on non-relativistic matter that interacts only gravitationally, that is, “cold” dark matter, The alternative possibilities advocated for solving small-scale problems of the standard scenario are based on the hypothesis that dark matter is made of warm particles that have a small, non-negligible thermal velocity, namely, “warm” dark matter.

“We found that the recent JWST detections of galaxies in the first fraction of a billion years after the Big Bang are valuable evidence for the nature of matter,” he says. it’s a statement Dr. Umberto Maio, a researcher at the Italian National Institute for Astrophysics (INAF) at the Trieste Astronomical Observatory, and lead author of the paper describing the discovery just published in Astronomy & Astrophysics.

Research shows that dark matter, the main component of matter in the universe, it is made of particles that are “cold” or slightly “warm” with a mass greater than 2 keV. Dark matter models with particle masses equal to or lighter than this limit are excluded from the study.

While previous work had ruled out the possibility of discriminating the nature of the matter using data from recent epochs, data from much older epochs and ad hoc numerical simulations – the basis of the new study – were needed to provide information on the statistical trends of primordial galaxies. and break the degenerations of the models.

“What we did was apply our Sophisticated new numerical implementation of early galaxy formation to interpret the latest JWST data“, says Dr. Maio. “We saw that, during the period when the first stars and galaxies are formed, the visible properties of the structures present in the universe depend on the mass of the dark matter particles.”

In fact, the study found evidence that the amount of cosmological star formation, ultraviolet luminosities, and molecular abundances vary in different dark matter models, and these variations can be contrasted with the latest data from the JWST, the first to arrive in the “old” universe.

“The study was based on the exceptional observations of galaxies in the first 500 million years detected with the JWST and published early in late 2022,” says Professor Matteo Viel from the International School for Advanced Studies in Trieste and co-author of the research. .

“This is an important application of scientific data at such primordial times to constrain the nature of dark matter. Thanks to JWST, we have observed the most distant galaxies in the universe and their properties tell us provide clear information about their constituents.”

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Written by Editor TLN

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