Galaxies fling out matter much more violently than we thought

Unexpectedly violent black holes may have sparked the mystery of missing cosmic matter.

Much of the universe is filled with mysterious dark matter, but even ordinary matter has escaped cosmologists. Some of these normal substances – made up of particles called baryons – seemed to go missing for a long time. Researchers have recently worked out where he was hiding, and now Boriana Hadziaska At the University of California, Berkeley and her colleagues learned how black holes may have shaped their distribution and obscured it.

“Matter consists of dark matter, which is the predominant component, and baryonic matter, or essentially gas. For this gas, only about a few percent is in the form of stars, and the rest is in the form of diffuse gas,” she says. The diffuse gas is dim and difficult to observe, but her team combined multiple observations to track it.

One data set they used shows how Baryon Matter casts a shadow on the remaining radiation from the Big Bang, the cosmic microwave background. Another key piece of the puzzle came from analyzing how assists are distorted by the gravitational fields of massive objects. By combining them, the team determined where dark matter and barium linger and where they disperse, both within and between galaxies.

Hadjiaska says it was interesting to find baryonic matter much larger than dark matter, indicating supermassive black holes at the centers of galaxies that would eject it in an unexpectedly violent manner.

“Understanding exactly how this process happens and how strong it is, so how much can be thrown out of a given galaxy [so far] remained extremely uncertain,” says Colin Hill at Columbia University in New York. Researchers can use computer simulations to model galaxies and their evolution, but to get that detail right, analyzes like this new one are critical, he says. “This gives us an additional probe to understand the role of supermassive black holes in moving gas around galaxies,” says Alex Krolevsky at the University of Waterloo in Canada.

Hadzhiyska says such an analysis could also help resolve the ongoing debate about the components of the universe – like ordinary matter and the invisible forests of dark matter that bind the universe together across the cosmos thanks to gravity. Her team now hopes to add even more types of observations to their analysis—for example, how short bursts of cosmic radio waves travel through diffuse baryon gas. An even better “baryon census” with less uncertainty is still needed, says Michael Shull at the University of Colorado Boulder.

Could this reveal some strangeness in the distribution of matter throughout the universe that would send theorists and models back to the drawing board? “We hope something breaks. I hope dark matter is where we start to see deviations [from the standard model of cosmology]“says Hadzhiyska.

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