Further evidence for a quasar-driven jet impacting its neighbour galaxy: the saga of HE0450−2958 continues

Abstract HE0450−2958, an interacting quasar–starburst galaxy pair at z = 0.285, is one of the best-known examples of strong star formation activity in the presence of a quasar-driven jet. We present new multiband Karl G. Jansky Very Large Array-imaging covering 1–6 GHz and reaching an angular resolution of up to 0.6 arcsec (a sixfold improvement over existing radio data). We confirm the previous detection of a spatially extended radio component around the quasar, indicating that there is ongoing star formation activity in the quasar host galaxy. For the first time, we directly detect a jet-like bipolar outflow from the quasar aligned with its companion star-forming galaxy (SFG) and several blobs of ionized gas in its vicinity identified in previous studies. Within the companion SFG, we find evidence for a flattening of the synchrotron spectral index towards the point of intersection with the jet axis, further suggesting that the outflow may actually be impacting its interstellar medium. We discuss two possible mechanisms that could have triggered the starburst in the companion SFG: a wet–dry merger with the quasar and jet-induced star formation. While triggering through interaction-driven gas dynamics cannot be excluded with current data, our new observations make HE0450−2958 a strong candidate for jet-induced star formation, and one of the rare links between local systems (like Minkowski's Object or Centaurus A) and the high-z regime where radio-optical alignments suggest that this phenomenon could be more common.