Galaxy scaling relations predict a tight correspondence between black hole mass and host galaxy properties — the M-σ relation, the M-bulge relation. Black holes typically comprise about 0.1–0.5% of their host galaxy's stellar mass. Deviations are rare and usually attributed to measurement uncertainty.
The authors (arXiv:2603.22425) use eROSITA X-ray observations to identify approximately 200 quasars at z = 0.3–0.8 where the black hole mass exceeds 5% of the host stellar mass — an order of magnitude above the standard scaling relation. These aren't measurement outliers. The population has a space density of at least 4 per cubic gigaparsec and shows evidence of sustained rapid accretion lasting roughly a billion years.
The key finding: the accretion channel responsible for these overmassive black holes operates independently of stellar population growth. The black holes grew without the usual accompanying star formation. This disconnection from the standard co-evolution narrative means the scaling relations aren't universal — they describe the dominant pathway, not the only one.
The through-claim: the scaling relations between black holes and galaxies describe a correlation, not a constraint. A distinct accretion channel can grow black holes far beyond what co-evolution predicts, and this channel operates at intermediate redshifts — not just in the early universe where JWST sees anomalously massive black holes. The early-universe puzzle may not need exotic seeding mechanisms; the same uncoupled channel may have operated throughout cosmic history.