27 Jun 2019

Abstract

Fast Radio Bursts (FRBs) are brief radio emissions from distant astronomical sources. Some are known to repeat, but most are single bursts. Non-repeating FRB observations have had insufficient positional accuracy to localize them to an individual host galaxy. We report the interferometric localization of the single pulse FRB 180924 to a position 4 kpc from the center of a luminous galaxy at redshift 0.3214. The burst has not been observed to repeat. The properties of the burst and its host are markedly different from the only other accurately localized FRB source. The integrated electron column density along the line of sight closely matches models of the intergalactic medium, indicating that some FRBs are clean probes of the baryonic component of the cosmic web.

[Image]

Fig. 2 Host galaxy of FRB 180924.

(A) VLT/FORS2 gʹ-band image showing the host galaxy of FRB 180924, labeled A. The burst location uncertainty is shown by the black circle. Two background faint background galaxies, labeled B and C, can be seen to the right and upper left are also visible (see supplementary text).

(B) Keck Cosmic Web Imager (KCWI) spectrum (17) of the FRB 180924 host, showing the detection of forbidden-line ionized oxygen emission [O II], and Calcium absorption which set the FRB redshift z = 0.3214. fλ is relative flux. The oxygen emission is attributed to gas ionized by a hard ionizing spectrum. The absorption lines are stellar.

(C) Section of Gemini Multi Object Spectrograph (GMOS) spectrum. The spectrum shows (Hydrogen) Balmer line Hα, Nitrogen, and Sulfur emission at a redshift consistent with the lines detected in the Keck spectrum.

(D) Section of GMOS spectrum showing detections of the Balmer line Hβ and forbidden line emission from doubly ionized Oxygen ([O III]).