When we think of galaxies, we often picture them as solitary, spinning disks of stars. However, the reality is far more intricate. Galaxies actually reside in cosmic neighborhoods called galaxy clusters, where hundreds of other galaxies are tightly bound together by gravity. These immense clusters typically feature a dominant central galaxy, which almost always hosts a supermassive black hole at its core.
More than just absorbers, black holes profoundly influence their galactic environments. They release near light-speed plasma jets that heat and stir the surrounding, millions-of-degrees-hot gas. This X-ray-emitting gas then dances in a cosmic ballet, a dynamic interplay of matter and energy that ultimately shapes galaxies.
Astronomers have been puzzled by this phenomenon, as the hot gas’s chemical composition surprisingly mirrors that of our Sun, leading to what’s known as the “solar paradox.”
At the University of Santiago, Dr. Valeria Olivares, an academic in the Department of Physics, is leading a Fondecyt Regular project to unravel the solar paradox. Her research aims to understand why the hot gas at the center of galaxy clusters has a chemical composition so remarkably similar to our Sun’s. By investigating the underlying physical and chemical processes, she seeks to determine how these interactions ultimately affect the formation and evolution of galaxies like our own Milky Way.
Solving this puzzle will help us better understand the chemical history of galaxies. “In that sense,” Dr. Olivares explains, “this project seeks to understand the formation and evolution of galaxies and the effects that phenomena such as the activity of supermassive black holes have on their development.”
Adding to this mystery are recent discoveries from the James Webb Space Telescope (JWST). Remarkably massive, metal-rich galaxies have been revealed in the very young universe, mere hundreds of millions of years after the Big Bang – an incredibly short timescale given the cosmos’ age. These findings significantly challenge current models of galaxy formation and raise profound new questions about the processes that enabled such rapid and enriched growth so early in cosmic history.
“Understanding these nearby environments could offer crucial clues about the formation of massive, metal-rich galaxies in the early cosmos,” she states. “This, in turn, would deepen our understanding of the universe’s history.”
The project will combine multi-wavelength observations and cutting-edge technologies, utilizing information inaccessible to single instruments. To study the hot gas around these galaxies, X-ray satellites such as Chandra and XMM-Newton will be employed, orbiting above Earth’s atmosphere, which otherwise blocks X-ray radiation.
These satellites can see gas at temperatures of millions of degrees and reveal what chemical elements it contains by analyzing its light. In addition, the new XRISM satellite will be used to measure the chemical composition of this gas with much greater precision and detail, identifying elements such as iron, oxygen, and silicon, which are fundamental to understanding its history.
Conversely, the MUSE instrument on the Very Large Telescope (VLT) in Chile’s Antofagasta Region will study central galaxies and their stellar populations. As one of the world’s most powerful observatories, the VLT’s MUSE instrument breaks down galactic light into an incredibly detailed spectrum, enabling analysis of stellar metal content and internal stellar motion.
Leveraging the unique conditions of the Chilean sky, the team will reconstruct this history by comparing the chemical composition of hot gas and stars. This will reveal how these components mix and enrich each other, providing crucial clues about the processes that shaped galaxies like the Milky Way.
Valeria Olivares emphasizes Chile’s importance: “Our exceptionally clear skies and the VLT in northern Chile are crucial for this project. They will allow us to compare the chemical composition of hot gas with that of the central galaxy’s stars, revealing their mutual enrichment.”
Groups of Small Galaxies
The project will also focus on smaller galaxy groups, where frequent interactions and mergers occur due to closer galactic proximity. This facilitates the mixing of gas and metals, potentially leading to new star formation.
“These collisions and interactions can displace gas, cool it, form new stars, or even feed the central black hole. All such events leave chemical traces within the system,” the researcher explains. “Understanding these processes will provide a much more complete picture of how galaxies, including the Milky Way, form and evolve.”
Beyond scientific research, the project actively trains new generations of astronomers. It engages undergraduate and graduate students in data reduction, analysis, and observation design.
The researcher concludes, “It’s very important that this project not only advances knowledge but also trains new astronomers. We seek to leave a legacy that supports future research and strengthens Chilean astronomy.”