No Significant Redshift Evolution in the Intrinsic Scatter of the $M_\bullet$-$M_\star$ Relation for Overmassive Black Holes

TL;DR

This study investigates whether the intrinsic scatter in the black hole mass versus stellar mass relation evolves with redshift, finding no significant change from the local universe to high redshift galaxies.

Contribution

It provides the first comprehensive analysis of the intrinsic scatter evolution across a wide redshift range, using diverse datasets.

Findings

No significant redshift evolution of the intrinsic scatter detected.

The intrinsic scatter remains consistent from local to high redshift.

Results suggest a stable co-evolution pattern of black holes and host galaxies.

Abstract

In the local Universe, the ratio between the mass of a central black hole and the stellar mass of its host galaxy is $\sim 0.1 \%$. 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 dataset. This Research Note examines whether a cosmic evolution of the intrinsic scatter can be detected by assessing its value for datasets in various redshift ranges. Using data from the local Universe ($z < 0.055$), low ($ 0.4 \leq z \leq 0.9$), intermediate ($ 0.9 \leq z \leq 4$), and high ($z > 4$) redshift, we conclude that there is no statistically significant redshift evolution of the intrinsic scatter.