Supermassive black holes were already enormous less than a billion years after the Big Bang — and we still don't fully understand how. One proposed explanation involved physical offsets between a black hole and the center of its host galaxy, caused by gravitational recoil after mergers or ongoing dynamical interactions. A new study tests this directly.

Researchers measured the positions of six quasars at redshift z > 6 with sub-arcsecond precision, combining two independent datasets. JWST NIRCam imaging traced the quasar's position — a proxy for the supermassive black hole — down to ~400 pc resolution. ALMA [C II] 158 ξm line emission and dust continuum mapped the host galaxy to better than 600 pc. Astrometric calibration was anchored to Gaia field stars within each NIRCam frame.

In all six systems, the black hole sits within the central ~400 pc of its host galaxy — well within measurement uncertainties. Apparent offsets seen in rest-frame optical JWST data disappear entirely when compared against ALMA, pointing to dust obscuration as the culprit rather than any true physical separation.

Kinematic modeling of the [C II] data adds another surprising finding: none of the six galaxies show signs of recent mergers. Most are well described by a rotating disk — a remarkably ordered structure for objects in such an early, turbulent Universe. The results support theoretical models predicting that black hole positional offsets are either extremely short-lived or intrinsically rare, even at cosmic dawn.