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Register a new userThe Fast Radio Burst Dispersion Measure Distribution
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We compare the dispersion measure (DM) statistics of FRBs detected by the ASKAP and Parkes radio telescopes. We jointly model their DM distributions, exploiting the fact that the telescopes have different survey fluence limits but likely sample the same underlying population. After accounting for the effects of instrumental temporal and spectral resolution of each sample, we find that a fit between the modelled and observed DM distribution, using identical population parameters, provides a good fit to both distributions. Assuming a one-to-one mapping between DM and redshift for an homogeneous intergalactic medium (IGM), we determine the best-fit parameters of the population spectral index, $hat{alpha}$, and the power-law index of the burst energy distribution, $hat{gamma}$, for different redshift evolutionary models. Whilst the overall best-fit model yields $hat{alpha}=2.2_{-1.0}^{+0.7}$ and $hat{gamma}=2.0_{-0.1}^{+0.3}$, for a strong redshift evolutionary model, when we admit the further constraint of $alpha=1.5$ we favour the best fit $hat{gamma}=1.5 pm 0.2$ and the case of no redshift evolution. Moreover, we find no evidence that the FRB population evolves faster than linearly with respect to the star formation rate over the DM (redshift) range for the sampled population.
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Fast radio bursts (FRBs) are millisecond pulses of radio emission of seemingly extragalactic origin. More than 50 FRBs have now been detected, with only one seen to repeat. Here we present a new FRB discovery, FRB 110214, which was detected in the high latitude portion of the High Time Resolution Universe South survey at the Parkes telescope. FRB 110214 has one of the lowest dispersion measures of any known FRB (DM = 168.9$pm$0.5 pc cm$^{-3}$), and was detected in two beams of the Parkes multi-beam receiver. A triangulation of the burst origin on the sky identified three possible regions in the beam pattern where it may have originated, all in sidelobes of the primary detection beam. Depending on the true location of the burst the intrinsic fluence is estimated to fall in the range of 50 -- 2000 Jy ms, making FRB 110214 one of the highest-fluence FRBs detected with the Parkes telescope. No repeating pulses were seen in almost 100 hours of follow-up observations with the Parkes telescope down to a limiting fluence of 0.3 Jy ms for a 2-ms pulse. Similar low-DM, ultra-bright FRBs may be detected in telescope sidelobes in the future, making careful modeling of multi-beam instrument beam patterns of utmost importance for upcoming FRB surveys.
Until very recently we had as many theories to explain Fast Radio Bursts as we have observations of them. An explosion of data is coming, if not here already, and thus it is an opportune time to understand how we can use FRBs for cosmology. The HIRAX experiment, based mostly in South Africa, will be one such experiment, designed not only to observe large numbers of FRBs but also to localise them. In this short article we consider briefly, some ways in which HIRAX can change the landscape of FRB cosmology.
The dispersion measure (DM) of fast radio bursts (FRBs) encode the integrated electron density along the line-of-sight, which is dominated by the intergalactic medium (IGM) contribution in the case of extragalactic FRBs. In this paper, we show that incorporating wide-field spectroscopic galaxy survey data in the foreground of localized FRBs can significantly improve constraints on the partition of diffuse cosmic baryons. Using mock DMs and realistic lightcone galaxy catalogs derived from the Millennium simulation, we define spectroscopic surveys that can be carried out with 4m and 8m-class wide field spectroscopic facilities. On these simulated surveys, we carry out Bayesian density reconstructions in order to estimate the foreground matter density field. In comparison with the `true matter density field, we show that these can help reduce the uncertainties in the foreground structures by $sim 2-3times$ compared to cosmic variance. We calculate the Fisher matrix to forecast that $N=30: (96)$ localized FRBs should be able to constrain the diffuse cosmic baryon fraction to $<10%: (<5%) $, and parameters governing the size and baryon fraction of galaxy circumgalactic halos to within $sim 15-20%: (sim 7-10%)$. From the Fisher analysis, we show that the foreground data increases the sensitivity of localized FRBs toward our parameters of interest by $sim 25times$. We briefly introduce FLIMFLAM, an ongoing galaxy redshift survey that aims to obtain foreground data on $sim 30$ localized FRB fields.
In this paper, we study the evolution of the ionization fraction $x_e(z)$ during the epoch of reionization by using the dispersion measurements (DMs) of fast radio bursts (FRBs). Different from the previous studies, here we turn to consider the large-scale clustering information of observed DMs of FRB catalog, which only needs the rough redshift distribution, instead of the exact redshift information of each FRB. Firstly, we consider the instantaneous ``texttt{tanh} model for $x_e(z)$ and find that including the auto-correlation information of the mock catalog, about $10^4$ FRBs with the intrinsic DM scatter of 100 $rm pc/cm^3$ spanning 20% of all sky, could significantly improve the constraint on the width $Delta_z$ of the model, when comparing with that from the CMB data alone. The evolution shape of the ionization fraction will be tightly narrowed, namely the duration of the epoch of reionization has been shrunk, $z_{rm dur}<2.24$ (95% C.L.). Furthermore, we also use another redshift-asymmetric reionization model and obtain that the FRB mock catalog could measure the ionization fraction at $z=6$ precisely with the $1sigma$ error $Delta x_e(z=6)=0.012$, which means that the large-scale clustering information of observed DMs of FRB catalog is very sensitive to the ionization fraction of the end of reionization epoch. We conclude that the observation of high-redshift FRBs could be a complementary probe to study the reionization history in the future.
We investigate the possibility of measuring intergalactic magnetic fields using the dispersion measures and rotation measures of fast radio bursts. With Bayesian methods, we produce probability density functions for values of these measures. We distinguish between contributions from the intergalactic medium, the host galaxy and the local environment of the progenitor. To this end, we use constrained, magnetohydrodynamic simulations of the local Universe to compute lines-of-sight integrals from the position of the Milky Way. In particular, we differentiate between predominantly astrophysical and primordial origins of magnetic fields in the intergalactic medium. We test different possible types of host galaxies and probe different distribution functions of fast radio burst progenitor locations inside the host galaxy. Under the assumption that fast radio bursts are produced by magnetars, we use analytic predictions to account for the contribution of the local environment. We find that less than 100 fast radio bursts from magnetars in stellar-wind environments hosted by starburst dwarf galaxies at redshift $z gtrsim 0.5$ suffice to discriminate between predominantly primordial and astrophysical origins of intergalactic magnetic fields. However, this requires the contribution of the Milky Way to be removed with a precision of $approx 1 rm~rad~m^{-2}$. We show the potential existence of a subset of fast radio bursts whose rotation measure carry information on the strength of the intergalactic magnetic field and its origins.
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