Redshift Evolution in Black Hole-Bulge Relations: Testing CIV-based Black Hole Masses

TL;DR

This study refines black hole mass estimates in lensed quasars using near-infrared spectroscopy, finding no significant evolution in black hole-bulge relations across redshifts, supporting the idea of overmassive black holes at high redshift.

Contribution

It provides improved black hole mass measurements using Balmer lines and evaluates the reliability of UV lines like CIV and CIII] for high-redshift estimates.

Findings

Large scatter between Balmer and UV line widths.

No systematic change in black hole masses with redshift.

CIII] may correlate with MgII, but needs further calibration.

Abstract

We re-examine claims of redshift evolution in black hole-bulge scaling relations based on lensed quasars. In particular, we refine the black hole mass estimates using measurements of Balmer lines from near-infrared spectroscopy obtained with Triplespec at Apache Point Observatory. In support of previous work, we find a large scatter between Balmer and UV line widths, both MgII 2796, 2803 and CIV 1548, 1550. There is tentative evidence that CIII] 1909, despite being a blend of multiple transitions, may correlate well with MgII, although a larger sample is needed for a real calibration. Most importantly, we find no systematic changes in the estimated BH masses for the lensed sample based on Balmer lines, providing additional support to the interpretation that black holes were overly massive compared to their host galaxies at high redshift.