New fast radio series shows scary signals from host galaxies

A new rapidly repeating radio eruption (FRB) has been identified in a dwarf galaxy. The newly discovered FRB has similar properties to the first-ranked one, but some differences suggest a different cosmic setting.

The first FRB was discovered in 2007 and named “Lorimer burst”, but the exact origin of many of them is still unknown.

Rapid radio bursts are pulses of radio frequency electromagnetic radiation. Radio emissions have durations on the order of milliseconds or faster and show the delay between bursts (a measure of scattering) characteristic of radio pulsars. They can be used as tools to study the material between galaxies, the intergalactic medium, but some may be better suited to probe the large gaps between galaxies, depending on the location of the FRB.

Publication of their results in Nature, researchers from the Chinese Academy of Sciences have discovered a new FRB, called FRB 20190520B, and identified its host galaxy, the dwarf galaxy known as J160204.31−111718.5. The dwarf galaxy has a relatively low redshift z = 0.241, corresponding to a distance from Earth of about 3,000 million light-years.


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The new FRB was detected with China’s Five Hundred Meter Aperture Spherical Telescope (FAST), the world’s largest parabolic antenna radio telescope, in operational scanning mode as part of the Commensal Radio Astronomy FAST Survey (CRAFTS) in 2019..

FRB 20190520B has many similarities with the Lorimer eruption, but its unique properties suggest that it lives in a different cosmic environment than other FRB sources.

corresponding author to Nature the article, Dr. Di Li, an astrophysicist at the Chinese Academy of Sciences, spoke Cosmos on the team’s results.

The source of the Lorimer eruption was never “heard” again, despite the initial “volume” of the signal and significant efforts to find it. About 500 different FRB sources have been identified, but only about 5% break out repeatedly, ”says Li.

To identify the new FRB’s host galaxy, the team superimposed their radio frequency observations on an optical image obtained using the Canada-France-Hawaii / MegaCam Telescope. See, they were able to identify the FRB’s home galaxy.

In (b), the Subaru / MOIRCS infrared J-band image only shows emission at the location of the top of the host galaxy’s optical light profile. The box is an area that coincides with the box at a. In (c), the VLA radio image shows a compact continuous source at the FRB site. Credit: D. Li et al.

The authors write that “although the contribution of the host galaxy to the dispersion target appears to be small for most FRBs”, there is at least one case where extreme properties of the host galaxy have altered the FRB proliferation target. .

Li says FRBs can tell us about the intergalactic medium by interacting with particles between galaxies. “The radio signal will be emitted by intergalactic electrons. Such a scattering will produce chirp in the burst signal, i.e. the delay in the arrival of lower frequencies of the same burst. By measuring the level of delay one can estimate the electron density involved and thus provide insight into this important component of cosmic matter. “

FRB 20190520B appears to be another case in which the host galaxy distorts the scattering measurement. Its host galaxy has its own competing radio source, and its spread measurement is almost an order of magnitude larger than other FRB host galaxies.

“FRB 20190520B has the highest confirmed electron density of any FRB environment. Together with the first known repeated FRB, FRB 20190520B is only the second source FRB with a persistent radio source counterpart. They could represent the youth of all FRBs in an evolving picture. “a possible correction by relating the spread of the signal to the intergalactic medium. For some sources, the local contribution may exceed the intergalactic medium,” Li explains.

The authors say this is reason to believe that detailing the characteristics of other rapid radio eruptions will have to involve examining the environment in which they live.

“Therefore, caution is advised in deriving redshifts for FRBs without precise identifications of host galaxies,” they write.

“Active repeaters are particularly useful for FRB research because they allow for more efficient tracking observations. The number of active repeaters remains in single digits. FRB 20190520B is so far the only one that is continuously active, that is, it never” sleeps “. The famous first repeater, FRB 20121102A, for example, can be extremely diligent when active, but then it is seen to” shut down “for several months. FRB No. 20190520B,” explains Li.

Li says he hopes astronomers can determine the origin of FRBs in the near future. “The Holy Grail in this field is the systematic capture of multiple wavelengths of explosive events. Given the pace of progress in this area, we can converge on a consistent picture of the astronomical origins of FRBs within a few years.”


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