A Fast Radio Burst Occurs Every Second throughout the Observable Universe

Abstract: Recent multi-telescope observations of the repeating Fast Radio Burst FRB 121102 reveal a Gaussian-like spectral profile and associate the event with a dwarf metal-poor galaxy at a cosmological redshift of 0.19. Assuming that this event represents the entire FRB population, we make predictions for the expected number counts of FRBs observable by future radio telescopes between 50 MHz and 3.5 GHz. We vary our model assumptions to bracket the expected rate of FRBs, and find that it exceeds one FRB per second per sky when accounting for faint sources. We show that future low-frequency radio telescopes, such as the Square Kilometer Array, could detect more than one FRB per minute over the entire sky originating from the epoch of reionization.

• The paper models fast radio bursts by leveraging FRB 121102’s Gaussian spectral profile to predict a cosmic occurrence rate exceeding one burst per second.
• It employs advanced spectral analysis and compares host galaxy demographics to refine the understanding of FRB luminosity distributions.
• The findings indicate that future instruments like the SKA could detect numerous high-redshift FRBs, providing new insights into cosmic evolution.

A Fast Radio Burst Occurs Every Second throughout the Observable Universe

Fast Radio Bursts (FRBs) have emerged as a prominent area of study within astrophysical research due to their enigmatic nature and potential cosmological applications. The paper "A Fast Radio Burst Occurs Every Second throughout the Observable Universe" by Fialkov and Loeb contributes to this area by proposing a model for predicting the occurrence rate of FRBs across cosmic volume. The study leverages the distinctive case of FRB 121102, a repeatable burst originating from a low-metallicity dwarf galaxy, to infer broader characteristics of the FRB population.

Core Model and Methodology

The paper utilizes multi-frequency observations of FRB 121102 to model the expected occurrence rate of FRBs. Exploiting the burst's unique Gaussian-like spectral profile associated with a redshift $z = 0.19$, the authors extend these characteristics to the entire FRB population. Their approach involves:

1. Spectral Analysis: Employing a Gaussian profile rather than a power-law model for the spectral distribution. This choice is based on the observations from the Very Large Array and Arecibo, which identified that FRB 121102's emissions do not fit well within the typical power-law framework.
2. Host Galaxy Demographics: The association of FRB 121102 with a metal-poor dwarf galaxy suggests that FRBs may predominantly originate from such low-metallicity environments. The study considers two scenarios: one where the host galaxies resemble FRB 121102’s host (low-mass, metal-poor), and another involving high-mass galaxies typical of lower redshifts.
3. Luminosity Functions: The paper explores both a delta function (standard candle) model and a Schechter function to capture varying degrees of intrinsic luminosity dispersion across the FRB population.

By applying these models, they infer that more than one FRB per second could be observable across the sky, with faint sources contributing significantly to this rate.

Numerical Results and Astronomical Implications

The predictions suggest that future radio telescopes, such as the Square Kilometer Array (SKA), will be capable of detecting an abundant number of FRBs, potentially exceeding one per minute. This high detection rate, especially predictions indicating a substantial number of FRBs from high-redshift epochs like the EoR, could provide novel insights into the distribution and characteristics of high-energy cosmic phenomena.

The analysis demonstrates that the shape of the FRB spectrum significantly influences detection rates. A Gaussian spectral profile, as opposed to a flat spectrum, results in a reduction of detectable high-redshift sources in lower frequency bands due to the redshift effect. However, this effect would necessitate low-frequency surveys to capture high-redshift events effectively.

Speculative Outlook and Future Directions

The paper opens several speculative avenues for future investigation. The possibility of utilizing FRBs to map the universe's ionization history, owing to their sensitivity to electron column density, provides a promising direction for cosmological studies. Moreover, the study underscores the necessity for advanced instrumentation capable of probing various spectral profiles across extensive redshift ranges. This capability is crucial, given the potential vastness of the FRB population, which could unlock insights into the characteristics of early-universe galaxies and the conditions of the intergalactic medium during the cosmic dawn.

In summary, Fialkov and Loeb provide a comprehensive framework for understanding FRB occurrence rates at a cosmic scale, presenting strong evidence that such phenomena are not only frequent but also pivotal in cosmological research. Their predictions, contingent upon advances in radio astronomy, are positioned to significantly impact our understanding of the universe's energetics and structure.