Oral Presentation

Statistical Inference of Fast Radio Burst Environments Using Galaxy Number Density: Similarities Between CHIME Repeaters and Non-Repeaters

Author(s): Vignesh Vavillakula Venkataramana Rao (NCHU), Tetsuya Hashimoto (NCHU), Tomotsugu Goto (NTHU), Shotaro Yamasaki (NCHU), Mohanraj Madheshwaran (NCHU), Tzu-Yin Hsu (NTHU), Sridhar Gajendran (NTHU), Simon C.-C. Ho (ANU), Terry Long Phan (NTHU), Hiroto Masaoka (NAOJ), and Amos Y.-A.Chen(NTHU)

Presenter: Vignesh Vavillakula venkataramana rao (National Chung Hsing University)

​​Fast Radio Bursts (FRBs) are brief yet highly energetic pulses of radio emission, the origin of which remains largely uncertain. FRBs are classified into two categories based on their repetition behavior: repeaters and non-repeaters. Distinct progenitor models have been proposed to account for these differences, with magnetars often associated with repeaters and cataclysmic events with non-repeaters. Therefore, elucidating the differences between these two populations is essential for constraining their underlying origins. However, the difficulty in accurately localizing FRBs has posed a significant challenge in confirming whether their progenitors are indeed distinct. In this study, we estimate the galaxy number density around FRBs listed in the CHIME catalog 1 by utilizing the WISE × PS1 galaxy catalog. Our methodology emphasizes the large-scale galactic environments surrounding FRBs, thereby it is independent of precise localization. This approach enables the inclusion of a significantly larger sample—26 repeaters and 238 non-repeaters—approximately twice the number of currently localized FRBs. If repeaters and non-repeaters originate in distinct galactic environments, it could imply different host and progenitor types. Conversely, similar environments might suggest a common progenitor. Here, we present our findings by comparing the density increments of both repeaters and non-repeater sources. The Kolmogorov-Smirnov (KS) test for the distributions of galaxy number densities around the FRB sources indicates no significant difference between repeaters and non-repeaters with a p-value of 0.32. Our finding suggests that repeaters and non-repeaters could share similar galactic environments and, hence, similar host and progenitor types. In addition to this, we find the majority of FRBs occur in underdense galactic environments compared to randomly selected regions, exhibiting a mild preference for young stellar populations.