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In recent years, millisecond duration radio signals originating from distant galaxies appear to have been discovered in the so-called Fast Radio Bursts. These signals are dispersed according to a precise physical law and this dispersion is a key observable quantity which, in tandem with a redshift measurement, can be used for fundamental physical investigations. While every fast radio burst has a dispersion measurement, none before now have had a redshift measurement, due to the difficulty in pinpointing their celestial coordinates. Here we present the discovery of a fast radio burst and the identification of a fading radio transient lasting $sim 6$ days after the event, which we use to identify the host galaxy; we measure the galaxys redshift to be $z=0.492pm0.008$. The dispersion measure and redshift, in combination, provide a direct measurement of the cosmic density of ionised baryons in the intergalactic medium of $Omega_{mathrm{IGM}}=4.9 pm 1.3%$, in agreement with the expectation from WMAP, and including all of the so-called missing baryons. The $sim6$-day transient is largely consistent with a short gamma-ray burst radio afterglow, and its existence and timescale do not support progenitor models such as giant pulses from pulsars, and supernovae. This contrasts with the interpretation of another recently discovered fast radio burst, suggesting there are at least two classes of bursts.
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We report on the host association of FRB 20181030A, a repeating fast radio burst (FRB) with a low dispersion measure (DM, 103.5 pc cm$^{-3}$) discovered by CHIME/FRB Collaboration et al. (2019a). Using baseband voltage data saved for its repeat bursts, we localize the FRB to a sky area of 5.3 sq. arcmin (90% confidence). Within the FRB localization region, we identify NGC 3252 as the most promising host, with an estimated chance coincidence probability $< 2.5 times 10^{-3}$. Moreover, we do not find any other galaxy with M$_{r} < -15$ AB mag within the localization region to the maximum estimated FRB redshift of 0.05. This rules out a dwarf host 5 times less luminous than any FRB host discovered to date. NGC 3252 is a star-forming spiral galaxy, and at a distance of $approx$ 20 Mpc, it is one of the closest FRB hosts discovered thus far. From our archival radio data search, we estimate a 3$sigma$ upper limit on the luminosity of a persistent compact radio source (source size $<$ 0.3 kpc at 20 Mpc) at 3 GHz to be ${rm 2 times 10^{26} erg~s^{-1} Hz^{-1}}$, at least 1500 times smaller than that of the FRB 20121102A persistent radio source. We also argue that a population of young millisecond magnetars alone cannot explain the observed volumetric rate of repeating FRBs. Finally, FRB 20181030A is a promising source for constraining FRB emission models due to its proximity, and we strongly encourage its multi-wavelength follow-up.
We calculate the dispersion measures (DMs) contributed by host galaxies of fast radio bursts (FRBs). Based on a few host galaxy observations, a large sample of galaxy with similar properties to observed ones has been selected from the IllustrisTNG simulation. They are used to compute the distributions of host galaxy DMs for repeating and non-repeating FRBs. For repeating FRBs, we infer the DM$ _{mathrm{host}} $ for FRBs like FRB 121102 and FRB 180916 by assuming that the burst sites are tracing the star formation rates in host galaxies. The median DM$_{mathrm{host}}$ are $35 (1+z)^{1.08}$ and $96(1+z)^{0.83}$ pc cm$^{-3}$ for FRBs like FRB 121102 and FRB 180916, respectively. In another case, the median of DM$_{mathrm{host}}$ is about $30 - 70$ pc cm$^{-3}$ for non-repeating FRBs in the redshift range $z=0.1-1.5$, assuming that the burst sites are the locations of binary neutron star mergers. In this case, the evolution of the median DM$_{mathrm{host}}$ can be calculated by $33(1+z)^{0.84}$ pc cm$^{-3}$. The distributions of DM$_{mathrm{host}}$ of repeating and non-repeating FRBs can be well fitted with the log-normal function. Our results can be used to infer redshifts of non-localized FRBs.
We present the discovery and subarcsecond localization of a new Fast Radio Burst with the Karl G. Jansky Very Large Array and realfast search system. The FRB was discovered on 2019 June 14 with a dispersion measure of 959 pc/cm3. This is the highest DM of any localized FRB and its measured burst fluence of 0.6 Jy ms is less than nearly all other FRBs. The source is not detected to repeat in 15 hours of VLA observing and 153 hours of CHIME/FRB observing. We describe a suite of statistical and data quality tests we used to verify the significance of the event and its localization precision. Follow-up optical/infrared photometry with Keck and Gemini associate the FRB to a pair of galaxies with $rm{r}sim23$ mag. The false-alarm rate for radio transients of this significance that are associated with a host galaxy is roughly $3times10^{-4} rm{hr}^{-1}$. The two putative host galaxies have similar photometric redshifts of $z_{rm{phot}}sim0.6$, but different colors and stellar masses. Comparing the host distance to that implied by the dispersion measure suggests a modest (~ 50 pc/cm3) electron column density associated with the FRB environment or host galaxy/galaxies.
Intense, millisecond-duration bursts of radio waves have been detected from beyond the Milky Way [1]. Their extragalactic origins are evidenced by their large dispersion measures, which are greater than expected for propagation through the Milky Way interstellar medium alone, and imply contributions from the intergalactic medium and potentially host galaxies [2]. Although several theories exist for the sources of these fast radio bursts, their intensities, durations and temporal structures suggest coherent emission from highly magnetised plasma [3,4]. Two sources have been observed to repeat [5,6], and one repeater (FRB 121102) has been localised to the largest star-forming region of a dwarf galaxy at a cosmological redshift of 0.19 [7, 8]. However, the host galaxies and distances of the so far non-repeating fast radio bursts are yet to be identified. Unlike repeating sources, these events must be observed with an interferometer with sufficient spatial resolution for arcsecond localisation at the time of discovery. Here we report the localisation of a fast radio burst (FRB 190523) to a few-arcsecond region containing a single massive galaxy at a redshift of 0.66. This galaxy is in stark contrast to the host of FRB 121102, being a thousand times more massive, with a greater than hundred times lower specific star-formation rate. The properties of this galaxy highlight the possibility of a channel for FRB production associated with older stellar populations.
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.
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