Fast radio bursts traveling across billions of light-years can be used to measure how ordinary matter is spread through the universe, according to a study published in Nature Astronomy. Led by graduate student Kritti Sharma alongside astronomy professor and coauthor Vikram Ravi, researchers analyzed a sample of about 100 fast radio bursts to directly measure the impact of galactic feedback on clumpy matter in large-scale cosmic regions, helping tackle longstanding challenges in measuring dark matter, dark energy, and the mass of neutrinos.
Measuring Universe Expansion With Fast Radio Bursts
Fast radio bursts originate during energetic events in distant galaxies, potentially from highly magnetized dead stars called magnetars, according to study findings. As these intense, brief flashes of radio light travel to Earth, they pass through intervening clouds of gas and matter. This process known as optical refraction spreads the colors of the burst out much like a prism turns sunlight into a rainbow, making shorter, bluer wavelengths arrive before longer, redder wavelengths.
The denser the fog the bursts travel through, the more their signals become dispersed. By examining about 100 of these flashes, researchers directly measured how galactic feedback—the gas and energy that galaxies push out into space—affects clumpy matter in the large-scale regions around and between galaxies. This measurement provides a clearer picture of cosmic structures that were previously muddied by internal galactic processes.
Untangling Galactic Feedback From Dark Matter and Dark Energy
To gain insights into the properties of dark matter and dark energy—a repulsive substance or force driving the accelerating expansion of the cosmos—researchers rely on sky surveys that chart how matter aggregates together. However, internal galactic feedback mechanisms can additionally alter the distribution density of matter, complicating the task for researchers trying to accurately quantify these cosmological influences. Supermassive black holes reside at the core of every galaxy, where they voraciously consume adjacent material while simultaneously expelling winds of heated, ionized gas into their environment alongside the energy released by stellar explosions.
“The feedback process thins the gas around the galaxies, redistributing matter across vast distances. It smooths out clumps of matter in a way that looks astonishingly similar to what massive neutrinos do, or what dark energy or dark matter theories predict,” Vikram Ravi said. “Unless scientists can independently measure this contribution from feedback, they can’t tell these effects apart.”
Did you know? While fast radio bursts were once difficult to interpret, analyzing their dispersion acts similarly to a prism, letting astronomers calculate the density of matter encountered over billions of light-years.
Comparing Fast Radio Burst Constraints With X-Ray and Microwave Surveys
The findings indicate that galactic feedback indeed creates a smoother distribution of surrounding material, reducing its clumpiness. Nevertheless, the extent of this smoothing falls short of earlier measurements obtained by advanced observing projects, which feature the eROSITA X-ray telescope as well as the now-concluded Atacama Cosmology Telescope in Chile, whose operations wrapped up in 2022.
“Our analysis of FRBs reveals how gas ejected by astrophysical feedback suppresses cosmic structure, delivering constraints competitive with X-ray and microwave surveys,” said coauthor Elisabeth Krause, a professor of astronomy and physics at the University of Arizona. Krause noted that this is amazing considering they only had about 100 FRBs in their sample, and it’s only the beginning.
Future Outlook With Caltech’s Deep Synoptic Array
Scheduled for completion by 2029 within an isolated Nevada valley, Caltech’s Deep Synoptic Array (DSA) is a high-performance radio telescope anticipated to detect tens of thousands of fast radio bursts, thereby significantly boosting the utility of these cosmic phenomena for refining cosmological assessments. Funded by Schmidt Sciences and co-led by Vikram Ravi, the array will work synergistically with several cosmology experiments.
Collaborative efforts will link data from the DSA with the European Euclid mission—featuring key contributions from NASA’s Jet Propulsion Laboratory and Caltech’s IPAC astronomy center—alongside Arizona’s Dark Energy Spectroscopic Instrument (DESI), the Vera Rubin Observatory located in Chile, and NASA’s recently deployed Nancy Grace Roman Telescope, which also involves vital participation from JPL and IPAC.
Frequently Asked Questions
What is a fast radio burst?
Fast radio bursts are intense, brief flashes of radio light originating from distant, energetic events across the universe.
How do fast radio bursts measure matter in the universe?
As bursts travel billions of light-years, intervening fog and clouds of gas disperse their signals similarly to how a prism splits white light, allowing scientists to calculate the density of matter along the path.
Why is galactic feedback a problem for cosmology?
Gas and energy ejected by galaxies smooth out surrounding matter in ways that look astonishingly similar to what massive neutrinos do, or what dark energy or dark matter theories predict, muddying researchers’ ability to precisely measure cosmological effects.
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