The First CHIME/FRB Fast Radio Burst Catalog (2106.04352v3)

Abstract: We present a catalog of 536 fast radio bursts (FRBs) detected by the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst (CHIME/FRB) Project between 400 and 800 MHz from 2018 July 25 to 2019 July 1, including 62 bursts from 18 previously reported repeating sources. The catalog represents the first large sample, including bursts from repeaters and non-repeaters, observed in a single survey with uniform selection effects. This facilitates comparative and absolute studies of the FRB population. We show that repeaters and apparent non-repeaters have sky locations and dispersion measures (DMs) that are consistent with being drawn from the same distribution. However, bursts from repeating sources differ from apparent non-repeaters in intrinsic temporal width and spectral bandwidth. Through injection of simulated events into our detection pipeline, we perform an absolute calibration of selection effects to account for systematic biases. We find evidence for a population of FRBs - comprising a large fraction of the overall population - with a scattering time at 600 MHz in excess of 10 ms, of which only a small fraction are observed by CHIME/FRB. We infer a power-law index for the cumulative fluence distribution of $\alpha=-1.40\pm0.11(\textrm{stat.})^{+0.06}_{-0.09}(\textrm{sys.})$, consistent with the $-3/2$ expectation for a non-evolving population in Euclidean space. We find $\alpha$ is steeper for high-DM events and shallower for low-DM events, which is what would be expected when DM is correlated with distance. We infer a sky rate of $[525\pm30(\textrm{stat.})^{+140}_{-130}({\textrm{sys.}})]/\textrm{sky}/\textrm{day}$ above a fluence of 5 Jy ms at 600 MHz, with scattering time at $600$ MHz under 10 ms, and DM above 100 pc cm$^{-3}$.

Insights into the First CHIME/FRB Fast Radio Burst Catalog

The CHIME/FRB collaboration has produced a comprehensive catalog of 536 fast radio bursts (FRBs) detected between July 2018 and July 2019 using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope. This catalog marks a significant advancement in the paper of FRBs, offering a consistent dataset to explore the properties and distributions of these enigmatic astronomical phenomena.

Key Findings and Methodology

1. Uniform Survey Methodology: The catalog represents the first large, uniform sample of FRBs, which includes both repeating and non-repeating sources. The uniformity of the survey allows for systematic comparison of FRB properties without the biases introduced by different observational techniques.
2. Properties of Repeaters and Non-repeaters: The catalog demonstrates that repeaters and apparent non-repeaters share consistent sky locations and dispersion measures (DMs), suggesting a similar origin. However, they differ significantly in their intrinsic temporal width and spectral bandwidth—repeaters are broader and more limited in bandwidth.
3. Selection Bias and Calibration: Systematic biases in detecting FRBs were addressed using simulated events injected into the detection pipeline, ensuring an absolute calibration of the selection effects. This process revealed a substantial yet scarcely observed population with a scattering time exceeding 10 milliseconds at 600 MHz.
4. Fluence Distribution: The cumulative fluence distribution was analyzed and found to have a power-law index of $\alpha = -1.40$, consistent with a non-evolving population in Euclidean space. This supports the notion that FRBs are cosmologically distributed.
5. Sky Rate and Implications: The inferred sky rate is significantly high, at approximately 525 FRBs per sky per day above a fluence of 5 Jy ms at 600 MHz. This finding underscores the ubiquity and cosmic significance of FRBs.

Theoretical and Practical Implications

The catalog facilitates further theoretical exploration of FRBs by providing an unprecedentedly large sample with homogeneous data collection methods. It supports the notion that FRBs may be cosmologically distributed phenomena and suggests diverse emission mechanisms between repeaters and non-repeaters. The differences in spectral properties between these two groups hint at potentially distinct astrophysical origins or stages of evolution within a single source class, raising questions regarding the environments and processes responsible for FRB emissions.

Future Developments

The CHIME/FRB catalog paves the way for further investigations into the relation between FRB properties and their host environments. Ongoing work includes polarimetry to understand the magnetic fields in FRB host environments, high-resolution studies to explore burst structures further, and cross-correlation with galaxy catalogs to better understand their spatial distribution.

This catalog serves as a foundational resource for the FRB research community, enabling the development of more complex models of FRB origins and their propagation through cosmic media. It highlights the need for continuous monitoring of FRBs across multiple wavelengths to unravel the complexities of these transient phenomena further. The CHIME/FRB collaboration plans to extend this research, including the release of their data for public use, thus fostering collaborative efforts to unlock the mysteries of fast radio bursts.