Extreme Values of Black Hole to Stellar Mass Ratio for High-Redshift Galaxies

Abstract

With recent data from the \emph{James Webb Space Telescope} (JWST), it is possible to calculate the mass of the supermassive black holes at the center of galaxies, and the stellar mass of the host galaxies at redshift $z\gtrsim 5$. In this work, we apply extreme-value statistics to calculate the distributions of extreme black-hole and stellar masses for galaxies in the redshift range $3\lesssim z\lesssim 8$. We show that under certain assumptions about the stellar and black-hole mass functions, a high ratio of $M_{\text{BH}}/M_{\ast }\sim 0.3-0.5$ can be obtained without invoking additional black-hole growth physics. Nevertheless, surveying a range of extreme-value methodologies, we find predictions of the extreme ratio $M_{\text{BH}}/M_{\ast }$ to still be in slight tension with the high values observed by JWST.

11 pages, 9 figures