Redshift evolution in black hole–bulge relations: Testing C IV-based black hole masses

We re-examine claims for redshift evolution in black hole–bulge scaling relations based on lensed quasars. In particular, we refine the black hole (BH) 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 Mg iiλλ2796, 2803 and C ivλλ1548, 1550. There is tentative evidence that C iii]λ1909, despite being a blend of multiple transitions, may correlate well with Mg ii, 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.