New evidence for the nature of matter from ancient galaxies in the early universe

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from the Astronomical Observatory of Trieste

The distribution of primordial matter in cosmological models with hot dark matter (WDM, left) and cold dark matter. Credit: CDM, right

Astrophysicists in Italy have shed new light on the nature of matter from the discovery of galaxies by the James Webb Telescope (JWST) from 13 billion years ago and modern numerical simulations of the first galaxies. The study adds another piece to the puzzle of the nature of matter in the universe.

While the generally accepted paradigm of structure formation is based on non-relativistic matter interacting only gravitationally, that is “cold” dark matter, alternative possibilities advocated to solve small-scale problems of the standard scenario rely on the hypothesis that dark matter is created. of warm particles possessing a small, non-negligible, thermal velocity, namely “warm” dark matter.

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

The research shows that dark matter, the main component of matter in the universe, consists of particles that are either “cold” or simply “warm” with a mass greater than 2 keV. Dark matter models with particle masses equal to or lighter than such limit are excluded from the study.

While previous work had ruled out the possibility of discriminating the nature of the issue using data from recent epochs, data from earlier times and ad hoc numerical simulations – the basis of the new study – were needed to provide information about trends. statistics of primordial galaxies and break the degeneracies of the models.

“What we did was apply our new, sophisticated, 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 form, the visible properties of the structures present in the universe depend on the mass of the dark matter particles.”

Indeed, 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 compared with the latest JWST data, the first to arrive at the “ancient” universe.

The research was a collaboration between the INAF Astronomical Observatory of Trieste and the International School for Advanced Studies of Trieste, Italy. “The study built on the remarkable observations of galaxies in the first half billion years discovered with JWST and released early in late 2022,” says Prof. 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 ages to constrain the nature of dark matter. Thanks to JWST we have observed the most distant galaxies in the universe and their properties give us clear information about their constituents. ”

This major achievement was made possible by JWST, which is an international collaboration between the US National Aeronautics and Space Administration (NASA), the European Space Agency (ESA) and the Canadian Space Agency (CSA). The research shows how two observables, the galaxy luminosity function and the galaxy correlation function on small scales of faint objects, especially when used in combination, are promising tools for discriminating between different dark matter models. The study’s findings are also consistent with the properties of the intergalactic medium, the “cosmic web,” at more recent epochs.

“In the future, when more data are available for small, faint and young sources, further hints may come from early statistics of stellar mass and carbon monoxide emission from galaxies,” they conclude. the scientists. The discovery of such early galaxies demonstrates that these structures can form in just a fraction of a billion years – which corresponds to the blink of an eye in cosmological contexts. Thus, more and more discoveries of primordial star-forming galaxies will be possible in the near future and this will pave the way for a better understanding of the nature of matter.

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

Journal information: Astronomy & Astrophysics

Provided by the Astronomical Observatory of Trieste