Enhanced Rates of Fast Radio Bursts from Galaxy Clusters

Abstract

Fast Radio Bursts (FRBs) have so far been detected serendipitously across the sky. We consider the possible enhancement in the FRB rate in the direction of galaxy clusters, and compare the predicted rate from a large sample of galaxy clusters to the expected cosmological mean rate. We show that clusters offer better prospects for a blind survey if the faint end of the FRB luminosity function is steep. We find that for a telescope with a beam of ∼ 1 deg 2 , the best targets would be either nearby clusters such as Virgo or clusters at intermediate cosmological distances of few hundred Mpc, which offer maximal number of galaxies per beam. We identify several galaxy clusters which have a significant excess FRB yield compared to the cosmic mean. The two most promising candidates are the Virgo cluster containing 1598 galaxies and located 16.5 Mpc away and S34 cluster which contains 3175 galaxies and is located at a distance of 486 Mpc.

Synthesising the intrinsic FRB population using frbpoppy

“…While work by e.g. Caleb et al (2016a) also adopt power law functions, recent work by Luo et al (2018) and Fialkov et al (2018) indicate a Schechter luminosity function might provide a more accurate description. While in this initial version of frbpoppy we only include a power law model, other distributions such as a Schechter luminosity function or a broken power law could be implemented in future iterations.…”

A fast radio burst in the direction of the Virgo Cluster

“…The field center is right ascension (RA) 12h33m and declination (Dec) +13d34m in the J2000 epoch. These coordinates were reported by Fialkov et al (2018) for the maximum FRB rates from Virgo. Fig.…”

“…The expected FRB number counts from Virgo depend on the shape of the luminosity function, cosmic FRB event rate (used for normalisation), the nature of the progenitors and the spectral energy distribution of the bursts. In Fialkov et al (2018) we considered two types of the luminosity function for FRBs: (i) standard candles with fixed luminosity of νL ν * = 2.8 × 10 43 erg s −1 which corresponds to the mean intrinsic luminosity of the observed FRBs (excluding the recently discovered ASKAP events); and (ii) the Schechter luminosity function. Fialkov et al showed that if FRBs are standard candles, the contribution of the supercluster is negligible compared to the cosmological contribution within the solid angle of Virgo.…”

“…The procedure is as follows: First, we follow the method outlined in Fialkov et al (2018) to calculate per-galaxy FRB event rate based on a cosmological population of FRBs as a function of α and L min and assuming a fixed total rate of N FRB = 10 4 FRBs per sky per day 3 above the detection threshold of 1 Jy out to redshift z = 1 (e.g., Nicholl et al 2017). Next, we apply this rate to Virgo galaxies extracted from an online Virgo catalogue (Kim et al 2014) and calculate the expected number of FRBs within the 300 h survey with ASKAP, N Virgo FRB .…”

“…While on-going blind large-area surveys are providing valuable insights into the population James et al 2018;James 2019), targeted searches can also prove fruitful. Recently, in one such attempt to optimise searches Fialkov et al (2018) predict a possible enhancement in the FRB rate in the direction of nearby galaxy clusters if the intrinsically faint FRB population is abundant. Their study was motivated by the availability of small (∼ 20 m class) radio telescopes which often have large amounts of observing time available with a modest (∼ 1 deg 2 ) field of view, but it can also be investigated by facilities with broader sky coverage.…”