Fast bursts of radio waves that originate millions to billions of light-years from Earth can be used as probes to study haloes of hard-to-see diffuse gas surrounding nearby galaxies.
New research shows that these pulses, called fast radio bursts (FRBs), slow as they pass through the gas surrounding galaxies between their source and Earth. This also has the effect of scattering their radio frequencies.
Using this to study galactic gas halos, researchers at the California Institute of Technology (Caltech) found twice as much material as previously thought in these envelopes that surround galaxies. This has implications for how these collections of stars and planets evolve over long periods of time.
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Astronomers looked at a sample of 474 distant FRBs with the Canadian Hydrogen Intensity Mapping Experiment (OUT), confirming that 24 FRBs intercepted by galactic halos were indeed delayed compared to others that traveled to Earth unhindered. Thus, this effect can be used to study the material through which the FRB passes.
“Our study shows that FRBs can act as skewers of all the matter between our radio telescopes and the source of the radio waves,” said Tolman, Caltech Astronomy Postdoctoral Fellow Liam Connor in statement (opens in new tab). “We used fast radio bursts to illuminate the halos of galaxies near the Milky Way and measure their hidden material.”
Using more distant FRBs outside our galaxy to probe the massive pools of gas that surround other galaxies has already revealed a surprise. Astronomers have found that there is more matter in the gas halos than previously thought, about twice as much as predicted by theoretical models.
“These gas tanks are huge,” Connor said. “If the human eye could see the spherical halo that surrounds the nearby Andromeda Galaxy, the halo would appear a thousand times larger than the moon.”
Because these gas halos are remnants of the same material used to form stars and planets, a deeper study of them could lead to a better understanding of how galaxies evolve over periods of billions of years.
Related: Scientists Discover Strange ‘Fast Radio Burst’ From Our Milky Way
An artist’s illustration shows the 300,000 light-year wide halo of gas that surrounds the Milky Way. (Image: NASA/CXC/M.Weiss; NASA/CXC/Ohio State/A.Gupta et al.)
Although researchers are currently unsure of the origin of FRBs, first detected in 2007, they believe that these pulses of electromagnetic radiation lasting from a fraction of a millisecond to several milliseconds are emitted by rapidly spinning magnetically dead stars. the so-called magnetars.
Evidence for this connection was provided in 2020 when Caltech’s Survey for Transient Astronomical Radio Emission 2 (STARE2) instrument teamed up with CHIME to detect a massive FRB erupting into the Milky Way.
Hundreds of FRBs have been observed since their discovery in 2007, and those discoveries are expected to keep rolling in thanks, in part, to Caltech’s 110 antenna Deep synoptic array (opens in new tab) or DSA-110.
The project has already identified several FRBs and traced them to the galaxies from which they originated. Caltech scientists have plans to build an even larger telescope in the coming years, which will consist of 2,000 dishes. Called DSA-2000, the project will be the most powerful radio observatory ever built and could detect and identify thousands of FRBs and their sources each year.
“This is just the beginning,” said Caltech assistant professor of astronomy Vikram Ravi. “As we discover more FRBs, our techniques can be applied to study individual haloes of different sizes and in different environments, addressing the unsolved problem of how matter is distributed in the Universe.”
The team’s research is published (opens in a new tab) in the journal Nature Astronomy.
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