This artist’s concept shows radio bursts fast and far through the halo of gas around galaxies in the local universe. Radio bursts were photographed traveling from the distant universe, through galactic halos, and finally reaching telescopes on Earth. The bumps seen in the two lines represent radio bursts as they move toward Earth. Credit: Courtesy of Charles Carter
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Powerful cosmic radio pulses emanating from the depths of the universe could be used to study hidden gas pools in nearby galaxies, according to a new study published last month in the journal. natural astronomy.
What is it called? fast radio blast, or FRBs, are pulses of radio waves typically from millions to billions of light years away. (Radio waves are electromagnetic radiation like light we see with our eyes but have a longer wavelength and lower frequency.) The first FRBs were discovered in 2007, and since then, hundreds of others have been discovered. In 2020, the STARE2 (Survey of Transient Astronomy Radio Emissions 2) instrument from the California Institute of Technology and CHIME (Canadian Hydrogen Intensity Mapping Experiment) from Canada Huge FRB Found In Our Milky Way Galaxy. These earlier findings helped confirm the theory that the energetic event most likely originated from a dead magnetar called a magnetar.
As more FRBs come in, scientists are now looking into how they can be used to study the gas between us and the eruption. In particular, they want to use FRBs to investigate the diffused gaseous halo surrounding the galaxy. As the radio pulses travel toward Earth, the gas enveloping the galaxy is expected to slow the waves and propagate radio frequencies. In the new study, the research team looked at a sample of 474 remote FRBs detected by CHIME, which has detected the most FRBs to date. They showed that the portion of the twenty FRBs that passed through the galactic halo actually slowed down more than the FRBs that did not.
“Our study shows that FRBs can serve as skewers for all materials between radio telescopes and radio wave sources,” said lead author Liam Connor, a Tolman postdoctoral researcher in astronomy, who worked with assistant professor of astronomy and co-author on the study, Vikram Ravi. .
“We used fast radio bursts to illuminate galactic halos near[{”attribute=””>MilkyWayandmeasuretheirhiddenmaterial”Connorsays[{”attribute=””>MilkyWayandmeasuretheirhiddenmaterial”Connorsays
The study also reports finding more matter around the galaxies than expected. Specifically, about twice as much gas was found as theoretical models predicted.
All galaxies are surrounded and fed by massive pools of gas out of which they were born. However, the gas is very thin and hard to detect. “These gaseous reservoirs are enormous. If the human eye could see the spherical halo that surrounds the nearby Andromeda galaxy, the halo would appear one thousand times larger than the moon in area,” Connor says.
Researchers have developed different techniques to study these hidden halos. For example, Caltech professor of physics Christopher Martin and his team developed an instrument at the W. M. Keck Observatory called the Keck Cosmic Webb Imager (KCWI) that can probe the filaments of gas that stream into galaxies from the halos.
This new FRB method allows astronomers to measure the total amount of material in the halos. This can be used to help piece together a picture of how galaxies grow and evolve over cosmic time.
“This is just the start,” says Ravi. “As we discover more FRBs, our techniques can be applied to study individual halos of different sizes and in different environments, addressing the unsolved problem of how matter is distributed in the universe.”
In the future, the FRB discoveries are expected to continue streaming in. Caltech’s 110-dish Deep Synoptic Array, or DSA-110, has already detected several FRBs and identified their host galaxies. Funded by the National Science Foundation (NSF), this project is located at Caltech’s Owen Valley Radio Observatory near Bishop, California. In the coming years, Caltech researchers have plans to build an even bigger array, the DSA-2000, which will include 2,000 dishes and be the most powerful radio observatory ever built. The DSA-2000, currently being designed with funding from Schmidt Futures and the NSF, will detect and identify the source of thousands of FRBs per year.
Reference: “The observed impact of galaxy halo gas on fast radio bursts” by Liam Connor and Vikram Ravi, 4 July 2022, Nature Astronomy.
DOI: 10.1038/s41550-022-01719-7
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