The dispersion measure of Fast Radio Bursts host galaxies: estimation from cosmological simulations

Abstract

ABSTRACT The dispersion measure (DM) of fast radio burst (FRB) encodes important information such as its distance, properties of intervening medium. Based on simulations in the Illustris and IllustrisTNG projects, we analyse the DM of FRBs contributed by the interstellar medium and circumgalactic medium in the hosts, DMhost. We explore two population models – tracing the star formation rate (SFR) and the stellar mass, i.e. young and old progenitors, respectively. The distribution of DMhost shows significant differences at z = 0 between two populations: the stellar mass model exhibits an excess at the low-DM end with respect to the SFR model. The SFR (stellar mass) model has a median value of 179 (63) pc cm−3 for galaxies with $M_*=10^{8\!-\!13}\, \mathrm{M}_{\odot }$ in the TNG100-1. Galaxies in the Illustris-1 have a much smaller DMhost. The distributions of DMhost deviate from lognormal function for both models. Furthermore, two populations differ moderately in the spatial offset from host galaxy’s centre in the stellar mass function of hosts. DMhost increases with the stellar mass of hosts when $M_* < 10^{10.5}\, \mathrm{M}_{\odot }$, and fluctuate at higher mass. At 0 < z < 2, DMhost increases with redshift. The differences in DMhost between two populations declines with increasing redshift. With more localized events available in the future, statistics such as DMhost, the offset from galaxy centre, and the stellar mass function of hosts will be of great helpful to ascertain the origin of FRB. Meanwhile, statistics of DMhost of localized FRB events could help to constrain the baryon physics models in galaxy evolution.