Deep Synoptic Array Science: A Massive Elliptical Host Among Two Galaxy-cluster Fast Radio Bursts

Abstract

The stellar population environments that are associated with fast radio burst (FRB) sources provide important insights for developing their progenitor theories. We expand the diversity of known FRB host environments by reporting two FRBs in massive galaxy clusters that were discovered by the Deep Synoptic Array (DSA-110) during its commissioning observations. FRB 20220914A has been localized to a star-forming, late-type galaxy at a redshift of 0.1139 with multiple starbursts at lookback times less than ∼3.5 Gyr in the A2310 galaxy cluster. Although the host galaxy of FRB 20220914A is similar to typical FRB hosts, the FRB 20220509G host stands out as a quiescent, early-type galaxy at a redshift of 0.0894 in the A2311 galaxy cluster. The discovery of FRBs in both late- and early-type galaxies adds to the body of evidence that the FRB sources have multiple formation channels. Therefore, even though FRB hosts are typically star-forming, there must exist formation channels that are consistent with old stellar population in galaxies. The varied star formation histories of the two FRB hosts that we report here indicate a wide delay-time distribution of FRB progenitors. Future work in constraining the FRB delay-time distribution, using the methods that we develop herein, will prove crucial in determining the evolutionary histories of FRB sources.

The Demographics, Stellar Populations, and Star Formation Histories of Fast Radio Burst Host Galaxies: Implications for the Progenitors

“…We supplement our sample of 23 FRB hosts with identified hosts of seven FRBs from the literature that did not meet the criteria for inclusion in our sample (a combination of low PATH probabilities were detected past the date cutoff of 2022 January, or have burst energetics below our cutoff) but nonetheless have claimed host identifications and redshifts. These include the CHIME FRB 20190425A (Panther et al 2023), DSA FRB 20190523A (Ravi et al 2019) (Connor et al 2023;Sharma et al 2023). We also plot a demarcation at νL ν = 10 9 L e below which a host can be classified as a dwarf galaxy (Figure 9).…”

“…Already, more FRBs are being found in these types of environments. Recent analysis from Sharma et al (2023) presented the first quiescent, elliptical FRB host galaxy association (FRB 20220509G), which is additionally part of the galaxy cluster Abell 2311. However, the connection between most FRBs and active star formation supports the young magnetar model theory, where magnetars are formed through the core-collapse supernovae of recently formed massive stars in the past 100 Myr, for the majority of FRBs.…”

Deep Synoptic Array Science: Implications of Faraday Rotation Measures of Fast Radio Bursts Localized to Host Galaxies

“…For 10% ( )  of sources, the magnetized intracluster medium (ICM) of galaxy clusters will contribute nonnegligibly to the observed RM. This can happen when the FRB sight line intersects a foreground galaxy cluster by chance (Lee et al 2023) as well as when the host galaxy is a cluster member Sharma et al 2023). DM and RM estimates for a sample of FRBs impacted by galaxy clusters will allow for magnetic-field constraints in the ICM, including beyond the virial radius where probes such as thermal X-ray emission are less sensitive.…”

“…Despite the small measurement uncertainty in the observed DMs (<0.06%), we assume for this analysis that the observed DM has a Gaussian distribution with standard deviation 0.1 pc cm −3 to account for any systematic errors (G. Chen et al 2023, in preparation). DM MW is taken to have a Gaussian distribution with standard deviation 30 pc cm −3 , DM MW,halo is taken to have a uniform distribution between 0 and 20 pc cm −3 , and DM IGM is distributed according to Zhang et al (2021) for each redshift; the redshift is treated as a constant given its negligible measurement uncertainty (<0.4%; Sharma et al 2023). The distribution of DM host (in the observer frame) is then given by the convolution below:…”

An X-Ray Census of Fast Radio Burst Host Galaxies: Constraints on Active Galactic Nuclei and X-Ray Counterparts

“…Technical upgrades to a number of FRB experiments in recent years have facilitated a small, but growing number of (sub)arcsecond localizations and robust host galaxy identifications for approximately three dozen events (e.g., Bhardwaj et al 2021;Kirsten et al 2022;Gordon et al 2023;Law et al 2023;Ravi et al 2023;Ryder et al 2023;Sharma et al 2023). The first population studies demonstrate that FRB hosts span a wide range of stellar masses and star formation rates (SFRs) and trace the underlying population of field galaxies (Heintz et al 2020;Bhandari et al 2022;Gordon et al 2023).…”