Tracing Radio AGN-Driven Quenching in Post-Starburst Galaxies at Cosmic Noon

We present a radio continuum study of photometrically selected cosmic noon (0.5 < z < 3) post-21 starburst galaxies (PSBs) in the UKIDSS Deep Survey (UDS) field to assess if radio-mode Active 22 Galactic Nuclei (AGN) are linked to the quenching of star formation at cosmic noon. Our cross-23 matching using the deep Very Large Array (VLA) imaging at 1.4 GHz results in a mean radio detection 24 fraction (f det) of only 0.8% for PSBs above a radio luminosity threshold of L 1.4 GHz ≥ 10 24 W Hz −1 , 25 increasing to 5±2% for massive PSBs with stellar masses M * > 10 11 M ⊙. Massive PSBs have a 26 comparable detection fraction to that of massive quiescent galaxies (f det = 8 ± 1%), and both classes 27 have lower fractions than that of massive star-forming galaxies (f det = 13 ± 1%) in the same field. The 28 radio luminosities of detected PSBs, L 1.4 ∼ 10 22.8 − 10 24.9 W/Hz, exceed those from star formation by 29 a median factor of 37 indicative of a possible AGN origin. Their compact morphologies (≲ 15 kpc 30 at z med = 1.5) suggest low-luminosity AGN with less powerful jets. Stacking the undetected PSBs 31 reveals a weak radio detection (3.9σ) in the highest mass bin (M * > 10 11 M ⊙). In contrast, 1.4 GHz 32 detected quiescent galaxies have radio luminosities reaching radio-loud levels, and a higher prevalence 33 of extended morphologies indicative of large-scale jetted AGN. The AGN contribution is also detected 34 in stacked measurements of quiescent galaxies. Overall, our results support a short radio AGN duty 35 cycle for PSBs, characterized by weak radio jets, suggesting radio-driven maintenance mode feedback 36 may become important at older ages. 37