Mapping Obscured Star Formation in the Host Galaxy of FRB 20201124A

Abstract

We present high-resolution 1.5–6 GHz Karl G. Jansky Very Large Array and Hubble Space Telescope (HST) optical and infrared observations of the extremely active repeating fast radio burst (FRB) FRB 20201124A and its barred spiral host galaxy. We constrain the location and morphology of star formation in the host and search for a persistent radio source (PRS) coincident with FRB 20201124A. We resolve the morphology of the radio emission across all frequency bands and measure a star formation rate (SFR) ≈ 8.9 M ⊙ yr−1, approximately ≈2.5–6 times larger than optically inferred SFRs, demonstrating dust-obscured star formation throughout the host. Compared to a sample of all known FRB hosts with radio emission, the host of FRB 20201124A has the most significantly obscured star formation. While HST observations show the FRB to be offset from the bar or spiral arms, the radio emission extends to the FRB location. We propose that the FRB progenitor could have formed in situ (e.g., a magnetar born from a massive star explosion). It is still plausible, although less likely, that the progenitor of FRB 20201124A migrated from the central bar of the host. We further place a limit on the luminosity of a putative PRS at the FRB position of L 6.0GHz ≲ 1.8 ×1027 erg s−1 Hz−1, among the deepest PRS luminosity limits to date. However, this limit is still broadly consistent with both magnetar nebulae and hypernebulae models assuming a constant energy injection rate of the magnetar and an age of ≳105 yr in each model, respectively.

A Fast Radio Burst in a Compact Galaxy Group at z ∼ 1

“…Ravi et al 2023a;Law et al 2023). This degree of precision allows for robust associations with host galaxies (Eftekhari & Berger 2017), allowing for identification of their host stellar population properties as observed in the rest-frame ultraviolet, optical, and infrared (e.g., Tendulkar et al 2017;Bannister et al 2019;Ravi et al 2019;Heintz et al 2020;Marcote et al 2020;Fong et al 2021;Bhandari et al 2022Bhandari et al , 2023Niu et al 2022;Ravi et al 2022Ravi et al , 2022Bhardwaj et al 2023;Eftekhari et al 2023;Ibik et al 2024;Law et al 2023;Sharma et al 2023), morphologies (Chittidi et al 2021;Mannings et al 2021;Tendulkar et al 2021;Xu et al 2022;Dong et al 2024), and galactocentric offsets (Heintz et al 2020;Mannings et al 2021;Bhandari et al 2022). The wealth of information uniquely enabled by host associations can provide strong constraints on FRB progenitor models via precise redshifts (therefore, rest-frame burst properties such as energetics) and properties of the local and global environments.…”