Observational Evidence of Positive Feedback from Radio Quasars

Feedback from active galactic nuclei (AGNs) is widely regarded as a key mechanism mediating the coevolution of supermassive black holes (SMBHs) and their host galaxies. Jets constitute a dominant channel of mechanical energy output and are associated with so-called “radio-mode” feedback. However, the net effect of “radio-mode” feedback—whether it suppresses or enhances star formation—remains observationally unresolved. Here we construct a sample of 1784 radio-detected quasars from the Dark Energy Spectroscopic Instrument (DESI), cross-matched with deep radio surveys: Low-Frequency Array (LOFAR) and Very Large Array Sky Survey (VLASS). We trace the star formation rate (SFR) in quasars' host galaxies across the jet lifetime. Our results reveal a statistically significant, monotonic rise-then-decline trend in the SFRs when jets evolve, which is consistent with hydrodynamical simulations predicting that jet-induced compression of the interstellar medium triggers star formation in its early phases. This trend remains statistically robust under rigorous multivariate control for key confounding parameters, including black hole mass, bolometric luminosity, and redshift. Collectively, our findings indicate that AGN radio jets exert positive influence on star formation over most of their evolutionary cycle.