Constraints from Galaxy-AGN Clustering on the Correlation between Galaxy and Black Hole Mass at Redshift 2 ≲ z ≲ 3

We use the clustering of galaxies around distant active galactic nuclei (AGNs) to derive an estimate of the relationship between galaxy and black hole mass that obtained during the ancient quasar epoch, at redshifts 2 ≲ z ≲ 3, when giant black holes accreted much of their mass. Neither the mean relationship nor its scatter differs significantly from what is observed in the local universe, at least over the ranges of apparent magnitude (16 ≲ G AB ≲ 26) and black hole mass (10 6 M ☉ ≲ M BH ≲ 10 10.5 M ☉ ) that we are able to probe.