The CHIME FRB population do not track the star formation history of the universe
The redshift distribution of fast radio bursts (FRBs) is not well constrained. The association of the Galactic FRB 200428 with the young magnetar SGR 1935+2154 raises the working hypothesis that FRB sources track the star formation history of the universe. The discovery of FRB 20200120E in association with a globular cluster in the nearby galaxy M81, on the other hand, casts doubts on such an assumption. We apply the Monte Carlo method developed in a previous work to test different FRB redshift distribution models against the recently released first CHIME FRB catalog in terms of their distributions in specific fluence, inferred isotropic energy, and external dispersion measure (DME). Our results clearly show that the hypothesis that all FRBs track the star formation history of the universe is ruled out. The hypothesis that all FRBs track the accumulated stars throughout history describes the data better but still cannot pass both the energy and DME criteria. The data seem to be better modeled with either a redshift distribution model invoking a significant delay with respect to star formation or a hybrid model invoking both a dominant delayed population and an insignificant star formation population. We discuss the implications of this finding for FRB source models.