Study explores the possibility that dark photons might be a heat source for intergalactic gas

Gas clouds across the universe are known to absorb the light produced by distant massive celestial objects, known as quasars. This light manifests as the so-called Lyman alpha forest, a dense structure composed of absorption lines that can be observed using spectroscopy tools.

Over the past decades, astrophysicists have been assessing the value of these absorption lines as a tool to better understand the universe and the relationships between cosmological objects. The Lyman alpha forest could also potentially aid the ongoing search for dark matter, offering an additional tool to test theoretical predictions and models.

Researchers at University of Nottingham, Tel-Aviv University, New York University, and the Institute for Fundamental Physics of the Universe in Trieste have recently compared low-redshift Lyman alpha forest observations to hydrodynamical simulations of the intergalactic medium and dark matter made up of dark photons, a renowned dark matter candidate.

Their paper, published in Physical Review Letters (PRL), builds on an earlier work by some members of their team, which compared simulations of the intergalactic medium (IGM) with Lyman-alpha forest measurements collected by the Cosmic Origins Spectrograph (COS) aboard the Hubble Space Telescope.

"In our analyses, we found that the simulation predicted line widths that were too narrow compared to the COS results, suggesting that there could be additional, noncanonical sources of heating occurring at low redshifts," Hongwan Liu, Matteo Viel, Andrea Caputo and James Bolton, the researchers who carried out the study, told Phys.org via email.

"We explored several dark matter models that could act as this source of heating. Building on two of the authors' experience with dark photons in a previous paper published in PRL, we eventually realized that heating from dark photon dark matter could work."

Based on their previous observations, Liu, Viel, Caputo and Bolton decided to alter a hydrodynamical simulation of the IGM (i.e., a sparse cloud of hydrogen that exists in the spaces between galaxies). In their new simulation, they included the effects of the heat that models predict would be produced by dark photon dark matter.

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