No Significant Redshift Evolution in the Intrinsic Scatter of the M •–M ⋆ Relation for Overmassive Black Holes

In the local Universe, the ratio between the mass of a central black hole and the stellar mass of its host galaxy is ∼0.1%. Recently, JWST discovered numerous galaxies at z > 4 that seem to deviate from the local relation, with black holes overmassive by 10–100 times. Similar galaxies were also discovered at cosmic noon. The intrinsic scatter in the relation describes how much the evolutionary histories of the single galaxies deviate from the mean evolutionary pattern of their parent data set. This Research Note examines whether a cosmic evolution of the intrinsic scatter can be detected by assessing its value for data sets in various redshift ranges. Using data from the local Universe (z < 0.055), low (0.4 ≤ z ≤ 0.9), intermediate (0.9 ≤ z ≤ 4), and high (z > 4) redshift, we conclude that there is no statistically significant redshift evolution of the intrinsic scatter.