The first galaxies could really mix it up!

An international team of researchers, most of whom have ties to KIPAC, has shown that the hot diffuse gas that fills the space between the galaxies has the same concentration of iron in all galaxy clusters that were studied in sufficient detail by the Japanese Suzaku satellite.

These results confirm the team's earlier findings regarding the Perseus Cluster, published in Nature, which suggested that most of the iron in the Universe was produced and spread throughout intergalactic space before galaxy clusters formed, more than 10 billion years ago. The iron, along with many other elements, was blown out of galaxies by the combined energy of billions of supernovae, as well as outbursts from growing supermassive black holes.

Multi-wavelength view of M82, a galaxy with very strong galactic winds. (Credit: NASA; Chandra, Spitzer, Hubble telescopes.)
M82, a nearby galaxy showing strong galactic winds. The early universe must have contained many more galaxies like this, or with even stronger activity.  X-ray data (Chandra) appears in blue; infrared data (Spitzer) appears in red; optical light (Hubble Space Telescope) appears in orange and yellow-green. (Credit: NASA, HST, Chandra, Spitzer Space Telescopes.)

The team studied the hot gas permeating ten nearby clusters of galaxies and showed that the concentration of chemical elements is about the same in all of them—a third of that observed in our Sun. This is surprising because the Sun is a relatively young star, with the benefit of generations of previous stars exploding and supplying iron for its formation, while it seems that most of the iron inside the intergalactic gas arose long before the first clusters of galaxies were even formed.

We have long known that most of the elements that we are made of were forged inside stars and released by these supernovae. However—how well the elements are spread through intergalactic space has long been an open question.

“If these elements were produced relatively recently, astronomically speaking, then we would expect a different concentration of iron from cluster to cluster. The fact that the distribution of iron appears so homogeneous, indicates that it has been produced by some of the first stars and galaxies that formed after the Big Bang,” says Ondrej Urban, the first author of the study, who was a KIPAC member and PhD student at Stanford University when he performed the extensive data analysis presented in the study.

“The remarkably uniform distribution of iron also means that the combined energy of many supernovae and the jets and winds of accreting supermassive black holes were able to mix the elements thoroughly across the universe,” says the corresponding author of the study, KIPAC alum Norbert Werner.

The results were presented at the annual meeting of the European Astronomical Society, EWASS 2017, in Prague, Czech Republic by Werner, leader of the MTA-Eötvös University Lendulet “Hot Universe” research group in Budapest and associate professor at the Masaryk University in Brno, Czech Republic and at Hiroshima University in Japan.The results are accepted for publication in the Monthly Notices of the Royal Astronomical Society.

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A uniform metal distribution in the intergalactic medium of the Perseus cluster of galaxies
A uniform metallicity in the outskirts of massive, nearby galaxy clusters