Abstract
We present the Australian Square Kilometre Array Pathfinder (ASKAP)
localization and follow-up observations of the host galaxy of the repeating FRB
20201124A, the fifth such extragalactic repeating fast radio burst (FRB) with
an identified host. From spectroscopy using the 6.5-m MMT Observatory, we
derive a redshift of $z=0.0979 0.0001$, SFR(H$\alpha$) $2.1
M_ødot$ yr$^-1$, and global metallicity of 12+log(O/H)$9.0$. By
jointly modeling the 12-filter optical-MIR photometry and spectroscopy of the
host, we infer a median stellar mass of $2 10^10 M_ødot$,
internal dust extinction of $A_V1-1.5$ mag, and a mass-weighted stellar
population age of $5-6$ Gyr. Connecting these data to the radio and
X-ray observations, we cannot reconcile the broad-band behavior with strong AGN
activity and instead attribute the dominant source of persistent radio emission
to star formation, likely originating from the circumnuclear region of the
host. The modeling also indicates a hot dust component contributing to the
mid-IR luminosity at a level of $10-30\%$. We construct the host
galaxy's star formation and mass assembly histories, finding that the host
assembled $>90\%$ of its mass by 1 Gyr ago and exhibited a fairly constant rate
of star formation for most of its existence, with no clear evidence of any
star-burst activity.
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