# The FRB 121102 host is atypical among nearby FRBs

## TL;DR

This study compares the host galaxies of nearby FRBs with those of the well-studied FRB 121102, revealing that FRB 121102's host is atypical and that common progenitor models like LGRBs and SLSNe may not apply to most nearby FRBs.

## Contribution

The paper introduces a galaxy-group-based method to estimate intergalactic electron density and demonstrates the diversity of FRB host galaxies, challenging previous assumptions about their progenitors.

## Key findings

- FRB 121102 host is consistent with LGRBs and SLSNe hosts.
- Nearby FRB hosts tend to have smaller $
m DM_{host}$ or are fainter.
- FRB 121102's host is atypical among nearby FRBs.

## Abstract

We search for host galaxy candidates of nearby fast radio bursts (FRBs), FRB 180729.J1316+55, FRB 171020, FRB 171213, FRB 180810.J1159+83, and FRB 180814.J0422+73 (the second repeating FRB). We compare the absolute magnitudes and the expected host dispersion measure $\rm DM_{host}$ of these candidates with that of the first repeating FRB, FRB 121102, as well as those of long gamma ray bursts (LGRBs) and superluminous supernovae (SLSNe), the proposed progenitor systems of FRB 121102. We find that while the FRB 121102 host is consistent with those of LGRBs and SLSNe, the nearby FRB host candidates, at least for FRB 180729.J1316+55, FRB 171020, and FRB180814.J0422+73, either have a smaller $\rm DM_{host}$ or are fainter than FRB121102 host, as well as the hosts of LGRBs and SLSNe. In order to avoid the uncertainty in estimating $\rm DM_{host}$ due to the line-of-sight effect, we propose a galaxy-group-based method to estimate the electron density in the inter-galactic regions, and hence, $\rm DM_{IGM}$. The result strengthens our conclusion. We conclude that the host galaxy of FRB 121102 is atypical, and LGRBs and SLSNe are likely not the progenitor systems of at least most nearby FRB sources. {The recently reported two FRB hosts differ from the host of FRB 121102 and also the host candidates suggested in this paper. This is consistent with the conclusion of our paper and suggests that the FRB hosts are very diverse. }