Interpretation of fast radio bursts from CHIME/FRB baseband data

Abstract

Fast radio bursts (FRBs) are radio pulses that originate from cosmological distances. Thousands of FRB sources have been discovered, but their origins remain unknown. Analyses of the energy function and redshift evolution of the volumetric event rate could provide crucial insights into FRB progenitors. In this paper, we used the $V_{\max }$ method to analyse the FRB energy functions and volumetric event rate evolution based on CHIME/FRB BaseCat 1 data. The baseband data provide improved fluence and bandwidth measurements compared to Catalogue 1, enabling a more robust analysis of FRB energy and population studies. The $V_{\max }$ method allows us to investigate volumetric event rate evolution as a function of redshift without any prior assumptions. The selection functions for baseband data were derived to re-weight the samples when calculating the number density. We observe Schechter-like shapes for the energy function with a unified slope index of $\gamma \in [-1.8,-1.6]$. Neither the cosmic star formation rate density (SFRD) nor the cosmic stellar-mass density scenario can be ruled out. We further discuss the scenario that FRBs are primarily produced from systems that evolve with a delay relative to SFRD. The rate evolution trend suggests a scenario of a delayed model with a delay time $\tau \approx 4.66$ Gyr, hinting at delayed core-collapse supernovae or compact binary mergers. Our work highlights the importance of baseband data, and the BaseCat 2 data are required to explore FRB populations and rate evolution.

arXiv comment14 pages,7 figures,2 tables. Accepted by A&A