Astronomers using ESO A very large telescope for the first time notices that a rapid burst of radio passes through a galactic halo. Continuing for less than a millisecond, this mysterious burst of cosmic radio waves passed almost unobstructed, suggesting that the halo had surprisingly low density and low magnetic field. This new technique can be used to explore the elusive haloes of other galaxies.
Using one cosmic mystery to probe another, astronomers analyzed the signal of a rapid burst of radio to shed light on diffuse gas in the halo of a massive galaxy . In November 2018, the Australian Telescope at Kilometer Array Pathfinder (ASKAP) identified a rapid burst of radio called FRB 181112. Subsequent observations with ESO's very large telescope (VLT) and other telescopes revealed that radio pulses had passed through the galaxy of a massive galaxy on the way to Earth. This finding allowed astronomers to analyze the radio signal for the nature of the halogen gas.
'The radio burst signal reveals the nature of the magnetic field around the galaxy and the structure of the halogen gas. The study proves a new and transformative technique for exploring the nature of galaxy galaxies, "says J. Xavier Prochaska, professor of astronomy and astrophysics at UC Santa Cruz and lead author of a paper presenting the new findings, published September 26, 2019, in the journal Science .
Astronomers still do not know what causes rapid radio bursts and have only recently been able to trace some of these very short, very bright radio signals back to the galaxies in which they originate. "When we were overlaying radio and optical images, we immediately realized that the rapid burst of radio had penetrated the halo of this foreground galaxy, and for the first time we had a direct way of exploring otherwise invisible matter around this galaxy," said Cherie Day co-author, Ph.D. in Swinburne, Australia.
A galactic halo contains matter that is dark and ordinary, or baryonic, hot ionized gas, while the luminous part of a massive galaxy can be about 30,000 light-years away. us, its roughly spherical halo is ten times larger in diameter. Halogen gas fuels star formation as it falls toward the center of the galaxy, while other processes, such as supernova explosions, can eject material from star-forming regions, One reason astronomers want to study the halogen gas is to better understand these ejection processes that can stop star formation.
"The halo of this galaxy is surprisingly calm," said Prochaska. "The radio signal was largely unaffected by the galaxy, which is in stark contrast to what previous models predict would occur upon the burst."
The signal of FRB 181112 consists of several pulses, each of which continues. less than 40 microseconds (10,000 times shorter than the blink of an eye). The short pulse duration places an upper limit on the density of the halogen gas, since passing through a denser medium would extend the duration of the radio signal. Researchers have estimated that the density of a halogen gas should be less than 0.1 atoms per cubic centimeter (equivalent to several hundred atoms in volume, the size of a baby balloon) .
"Like the glistening hot air of a summer day, the weak atmosphere in this massive galaxy must distort the signal for the rapid burst of radio. Instead, we received a pulse so virgin and sharp that there was no signature of this gas at all, "says co-author Jean-Pierre McAuart, an astronomer at the International Center for Radio Astronomy Research at Curtin University, Australia.
There is no evidence of cold storm clouds or small The rapid burst of radio also gives information about the magnetic field in the halo, which is very weak – a billion times lower than that of a refrigerator magnet.
At this point, with results from only one galactic halo, the researchers do not may say if the low density and low magnetic field strength they measure are unusual or if previous studies of galactic halos have overestimated these properties, Prachak said he expects ASCAP and other radio telescopes to use fast radio explosions to study many more galactic
"This galaxy may be special," he said. "We'll have to use fast radio shots to study dozens or hundreds of galaxies in a range of masses and epochs to evaluate the full realm. "Optical telescopes such as ESO VLT to play an important role in revealing how far away the galaxy that has played as host each burst is and whether the outbreak would pass through the halo of any galaxy in the foreground.
 A huge halo of low gas density extends far beyond the glowing part of the galaxy where the stars are concentrated. Although this hot, diffuse gas represents a larger mass of the galaxy than the stars, it is very difficult to study.
 Density constraints also limit the possibility of turbulence or clouds of cool gas in the halo. Cool here is a relative term referring to temperatures of about 10,000 ° C, compared to hot halogen gas at about 1 million degrees.
This study was presented in a document published on September 26, 2019 in the journal Science .
The team is composed of J. Xavier Prachaska (University of California Observatories-Lik Observatory, University of California, USA and Institute of Physics and Mathematics of the Universe, Japan), Jean-Pierre Macquart (International Center for Radio Astronomy Research, McQuinn University, Matthew Kurtin University) in Astronomy, University of Washington, USA), Sunil Simha (University of California Observatories-Lik Observatory, University of California, USA), Ryan M. Shannon (Center for Astrophysics and Supercomputers, Swinburne University of Technology, Australia), Cherry K. Day (Center for Astrophysics and Supercomputers, Swinburne University of Technology, Australia and Commonwealt h Organization for Scientific and Industrial Research, National Telescope Facility) , Lachlan Marnoch (Community Science and Industrial Research Organization, Australian National Telescope Facility, Australia and Department of Physics and Astronomy, Macquarie University, Australia), Stuart Ryder (Department of Physics and Astronomy, Univ Macquarie University, Australia), Adam Dehler (Center for Astrophysics and Supercomputing, Swinburne University of Technology, Australia), Keith W. Banister (Community Science and Industrial Research Organization, National Telescope Fund of Australia, Australia), Shivani Bhandari Commonwealth Organization for Scientific and Industrial Research, National Telescope Fund of Australia, Australia), Rongmon Bordoloi (North Carolina State University, Department of Physics, USA), John Bunton (Commo Research and Industrial Organization) nwealth, National Telescope National Fund, Australia), Hyerin Cho (School of Physics and Chemistry, Gw Anjou Institute of Science and Technology, Korea), Chris Flynn (Center for Astrophysics and Supercomputing, Swinburne University of Technology, Australia), Elizabeth Mahoney ( Commonwealth Research and Industrial Research Organization, National Telescope National Fund, Australia), Chris Phillips (Commonwealth Science and Industrial Research Organization, National Telescope Fund in Australia, Australia), Hao Qiu (Sydney Institute of Astronomy, School of Physics) , University of Sydney, Aus Rally), Nicolas Teyos (Instituto de Fisica, Pontificia Universidad Catolica de Valparaiso, Chile).  Reference: "Low density and magnetization of a massive galactic halo exposed to rapid radio explosion" (PDF) by J. Xavier Prochaska, Jean-Pierre Macquart, Matthew McQuinn, Sunil Simha, Ryan M. Shannon, Cherie K. Day, Lachlan Marnoch, Stuart Ryder, Adam Deller, Keith W. Bannister, Shivani Bhandari, Rongmon Bordoloi, John Bunton, Hyerin Cho, Chris Flynn, Elizabeth K. Mahony, Chris Phillips, H ao Qiu and Nicolas Tejos, September 26, 2019, Science .
doi: 10.1126 / science.aay0073