Zooming in on Fast Radio Bursts

New research published in ApJL today describes the global properties of the first sample of host galaxies of apparently non-repeating fast radio bursts (FRBs) localized by ASKAP.

This study is a step forward in understanding the type of galaxies that FRBs come from and also their astrophysical origin. There are many different theories about how FRBs are caused. Some of these involve cataclysmic events such as stellar explosions or the merger of two compact objects involving neutron stars or black holes, while others such as giant electromagnetic flares from pulsars and magnetars could explain the ‘repeating’ nature of some of the FRBs.

Localising FRBs to their host galaxies is an essential first step in working out which of these theories can best explain the observations. ASKAP is playing a pivotal role in FRB localisations enabling the identification of their host galaxies. The four precisely localised busts presented by Bhandari et al. came from the outskirts of their host galaxies, ruling out models involving supermassive black holes which live at the centres of these galaxies.

ESO’s Very Large Telescope was used to image the host galaxies, zooming in on the locations pinpointed by ASKAP. Additional follow-up observations conducted with optical telescope such as Keck II and Gemini South established the distance to the host galaxies and studied properties such as colour magnitudes, mass, size and star formation rate.

All four FRB hosts are massive galaxies, roughly the same size as the Milky Way and making stars sedately. Some earlier work suggested that most FRBs could be a by-product of a special class of exploding stars known as `super-luminous supernovae’ that are mainly found in very small ‘dwarf’ galaxies.

This latest research shows that while one FRB (the ‘repeating’ FRB 121102) is known to lie in a dwarf galaxy, this is rather unusual in terms of the general FRB population.

CSIRO’s ATCA telescope and NRAO’s Very Large Array also studied the radio environment of these FRBs in their host galaxies and found that none were embedded in a dense radio nebula.

Thus, FRBs can originate in more diverse environments than previously thought. ASKAP is leading the world in localisation of FRBs and finding their home galaxies. More localisations and understanding of the FRB hosts and the immediate environments of the FRB will ultimately solve the puzzle of what causes these short but energetic events.

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