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Register a new userCosmology-insensitive estimate of IGM baryon mass fraction from five localized fast radio bursts
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Five fast radio bursts (FRBs), including three apparently non-repeating ones FRB 180924, FRB 181112, and FRB 190523, and two repeaters, FRB 121102 and FRB 180916.J0158+65, have already been localized so far. We apply a method developed recently by us (Li et al. 2019) to these five localized FRBs to give a cosmology-insensitive estimate of the fraction of baryon mass in the IGM, $f_{rm IGM}$. Using the measured dispersion measure (DM) and luminosity distance $d_{rm L}$ data (inferred from the FRB redshifts and $d_{rm L}$ of type Ia supernovae at the same redshifts) of the five FRBs, we constrain the local $f_{rm IGM} = 0.84^{+0.16}_{-0.22}$ with no evidence of redshift dependence. This cosmology-insensitive estimate of $f_{rm IGM}$ from FRB observations is in excellent agreement with previous constraints using other probes. Moreover, using the three apparently non-repeating FRBs only we get a little looser but consistent result $f_{rm IGM} = 0.74^{+0.24}_{-0.18}$. In these two cases, reasonable estimations for the host galaxy DM contribution (${rm DM_{host}}$) can be achieved by modelling it as a function of star formation rate. The constraints on both $f_{rm IGM}$ and ${rm DM_{host}}$ are expected to be significantly improved with the rapid progress in localizing FRBs.
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The excessive dispersion measure (DM) of fast radio bursts (FRBs) has been proposed to be a powerful tool to study intergalactic medium (IGM) and to perform cosmography. One issue is that the fraction of baryons in the IGM, $f_{rm IGM}$, is not properly constrained. Here we propose a method of estimating $f_{rm IGM}$ using a putative sample of FRBs with the measurements of both DM and luminosity distance $d_{rm L}$. The latter can be obtained if the FRB is associated with a distance indicator (e.g. a gamma-ray burst or a gravitational wave event), or the redshift $z$ of the FRB is measured and $d_{rm L}$ at the corresponding $z$ is available from other distance indicators (e.g. type Ia supernovae) at the same redshift. Since $d_{rm L}/{rm DM}$ essentially does not depend on cosmological parameters, our method can determine $f_{rm IGM}$ independent of cosmological parameters. We parameterize $f_{rm IGM}$ as a function of redshift and model the DM contribution from a host galaxy as a function of star formation rate. Assuming $f_{rm IGM}$ has a mild evolution with redshift with a functional form and by means of Monte Carlo simulations, we show that an unbiased and cosmology-independent estimate of the present value of $f_{rm IGM}$ with a $sim 12%$ uncertainty can be obtained with 50 joint measurements of $d_{rm L}$ and DM. In addition, such a method can also lead to a measurement of the mean value of DM contributed from the local host galaxy.
In this paper we propose the model that the coalescence of primordial black holes (PBHs) binaries with equal mass $M sim 10^{28}$g can emit luminous gigahertz (GHz) radio transient, which may be candidate sources for the observed fast radio bursts (FRBs), if at least one black hole holds appropriate amount of net electric charge $Q$. Using a dimensionless quantity for the charge $q = Q/sqrt{G}M$, our analyses infer that $qsim O(10^{-4.5})$ can explain the FRBs with released energy of order $O(10^{40}) {rm ergs}$. With the current sample of FRBs and assuming a distribution of charge $phi(q)$ for all PBHs, we can deduce that its form is proportional to $q^{-3.0pm0.1}$ for $qgeq 7.2times10^{-5}$ if PBHs are sources of the observed FRBs. Furthermore, with the proposed hypothetical scenario and by estimating the local event rate of FRBs $sim 2.6 times 10^3 {rm Gpc}^{-3} {rm yr}^{-1}$, one derives a lower bound for the fraction of PBHs (at the mass of $10^{28}$g) against that of matter $f_{rm PBH}(10^{28}{rm g})$ $gtrsim 10^{-5}$ needed to explain the rate. With this inspiring estimate, we expect that future observations of FRBs can help to falsify their physical origins from the PBH binaries coalescences. In the future, the gravitational waves produced by mergers of small black holes can be detected by high frequency gravitational wave detectors. We believe that this work would be a useful addition to the current literature on multimessenger astronomy and cosmology.
Several fast radio bursts have been discovered recently, showing a bright, highly dispersed millisecond radio pulse. The pulses do not repeat and are not associated with a known pulsar or gamma-ray burst. The high dispersion suggests sources at cosmological distances, hence implying an extremely high radio luminosity, far larger than the power of single pulses from a pulsar. We suggest that a fast radio burst represents the final signal of a supramassive rotating neutron star that collapses to a black hole due to magnetic braking. The neutron star is initially above the critical mass for non-rotating models and is supported by rapid rotation. As magnetic braking constantly reduces the spin, the neutron star will suddenly collapse to a black hole several thousand to million years after its birth. We discuss several formation scenarios for supramassive neutron stars and estimate the possible observational signatures {making use of the results of recent numerical general-relativistic calculations. While the collapse will hide the stellar surface behind an event horizon, the magnetic-field lines will snap violently. This can turn an almost ordinary pulsar into a bright radio blitzar: Accelerated electrons from the travelling magnetic shock dissipate a significant fraction of the magnetosphere and produce a massive radio burst that is observable out to z>0.7. Only a few percent of the neutron stars needs to be supramassive in order to explain the observed rate. We suggest that fast radio bursts might trace the solitary formation of stellar mass black holes at high redshifts. These bursts could be an electromagnetic complement to gravitational-wave emission and reveal a new formation and evolutionary channel for black holes that are not seen as gamma-ray bursts. Radio observations of these bursts could trace the core-collapse supernova rate throughout the universe.
Fast radio bursts (FRBs) probe the total column density of free electrons in the intergalactic medium (IGM) along the path of propagation though the dispersion measures (DMs) which depend on the baryon mass fraction in the IGM, i.e., $f_{rm IGM}$. In this letter, we investigate the large-scale clustering information of DMs to study the evolution of $f_{rm IGM}$. When combining with the Planck 2018 measurements, we could give tight constraints on the evolution of $f_{rm IGM}(z)$ from about $10^4$ FRBs with the intrinsic DM scatter of $30(1+z)~ rm pc/cm^3$ spanning 80% of the sky and redshift range $z=0-3$. Firstly, we consider the Taylor expansion of $f_{rm IGM}(z)$ up to second order, and find that the mean relative standard deviation $sigma(f_{rm IGM})equivleftlangle sigma[f_{rm IGM}(z)] /f_{rm IGM}(z) rightrangle$ is about 7.2%. In order to alleviate the dependence on fiducial model, we also adopt a non-parametric methods in this work, the local principle component analysis. We obtain the consistent, but weaker constraints on the evolution of $f_{rm IGM}(z)$, namely the mean relative standard deviation $sigma(f_{rm IGM})$ is 24.2%. With the forthcoming surveys, this could be a complimentary method to investigate the baryon mass fraction in the IGM.
We detail a new fast radio burst (FRB) survey with the Molonglo Radio Telescope, in which six FRBs were detected between June 2017 and December 2018. By using a real-time FRB detection system, we captured raw voltages for five of the six events, which allowed for coherent dedispersion and very high time resolution (10.24 $mu$s) studies of the bursts. Five of the FRBs show temporal broadening consistent with interstellar and/or intergalactic scattering, with scattering timescales ranging from 0.16 to 29.1 ms. One burst, FRB181017, shows remarkable temporal structure, with 3 peaks each separated by 1 ms. We searched for phase-coherence between the leading and trailing peaks and found none, ruling out lensing scenarios. Based on this survey, we calculate an all-sky rate at 843 MHz of $98^{+59}_{-39}$ events sky$^{-1}$ day$^{-1}$ to a fluence limit of 8 Jy-ms: a factor of 7 below the rates estimated from the Parkes and ASKAP telescopes at 1.4 GHz assuming the ASKAP-derived spectral index $alpha=-1.6$ ($F_{ u}propto u^{alpha}$). Our results suggest that FRB spectra may turn over below 1 GHz. Optical, radio and X-ray followup has been made for most of the reported bursts, with no associated transients found. No repeat bursts were found in the survey.
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