Strong radio pulse Origins deep in the universe could be used to study hidden puddles of nearby galaxies, according to a new study appearing in the journal Nature. Natural Astronomy.
Color composite image of Centaurus A, revealing lobes and sparks emanating from the central black hole of the active galaxy. Image credits: ESO/WFI (Optics); MPIfR / ESO / APEX / A.Weiss et al. (Submillimetre); NASA / CXC / CfA / R.Kraft et al. (X-ray) through WikimediaCC-BY-4.0
So-called fast radio bursts, or FRBs, are pulses of radio waves that typically originate in millions to billions of light-years (radio waves are electromagnetic radiation like the light we see with our eyes but longer wavelengths and frequencies). The first FRB was discovered in 2007, and since then, hundreds more have been found. In 2020, Caltech’s STARE2 (Transient Astronomical Radio Emission Survey 2) and Canada’s CHIME (Canadian Hydrogen Intensity Mapping Experiment) instrument discovered a giant FRB has erupted in our own Milky Way. These earlier results helped confirm the theory that energetic events most likely originate from dead, magnetized stars known as magnets.
As more and more FRBs emerge, researchers are now asking how they can be used to study the gas between us and the explosions. In particular, they want to use the FRB to probe the halos of diffuse gas that surround galaxies. As the radio pulses travel towards Earth, the gas surrounding the galaxies is thought to slow down the waves and scatter the radio frequencies. In the new study, the researchers looked at a sample of 474 distant FRBs detected by CHIME, the most FRBs detected to date, and showed that a subset of two dozen FRBs pass through the halo. The galaxy is actually slowed down more than the non-intersecting FRBs.
“Our study shows that the FRB can act as an oblique object between our radio telescope and the source of radio waves,” said lead author Liam Connor, Research Associate PhD in Astronomy Tolman , who works with assistant professor of astronomy and study co-author, Vikram Ravi.
“We used fast radio bursts to shine light through the halos of galaxies near the Milky Way and measure their hidden matter,” says Connor.
The study also reported finding more matter around the galaxies than expected — specifically, twice as much gas as theoretical models had predicted.
All galaxies are surrounded and nourished by the huge pools of gas from which they are born. However, the gas is very thin and difficult to detect. “These gas reservoirs are huge. If the human eye could see the spherical halo surrounding the nearby Andromeda galaxy, this halo would appear a thousand times larger than the moon,” Connor said.
Researchers have developed different techniques to study hidden halos. For example, Caltech physics professor Christopher Martin and his team have developed an instrument at the WM Keck Observatory called the Keck Cosmic Webb Imager (KCWI) that can probing filaments of gas flowing into galaxies from halos.
This new FRB method allows astronomers to measure the total amount of matter in the halo, helping to piece together a picture of how galaxies grow and evolve over cosmic time.
“This is just the beginning,” says Ravi. “As we detect more FRBs, our techniques can be applied to study individual halos of different sizes and in different environments, solving an unsolved problem. decide on the distribution of matter in the universe.”
Written by Whitney Clavin
Source: Caltech
