In Search of the Largest Velocity Dispersion Galaxies

We present Hobby-Eberly Telescope (HET) observations for galaxies at redshift [image] from the Sloan Digital Sky Survey (SDSS) showing large velocity dispersions while appearing to be single galaxies in HST images. The high signal-to-noise HET spectra provide more definitive velocity dispersions. The maximum velocity dispersion we find is [image] km s super(-1). Emission-line widths in QSOs indicate that black holes can exist with masses M sub([dot]) exceeding 5 billion M sub([image]), implying [image] km s super(-1) by the local M sub([dot])- capital sigma sub(*) relationship. This suggests either that QSO black hole masses are overestimated or that the black hole- bulge relationship changes at high black hole mass. The latter option is consistent with evidence that the increase in capital sigma sub(*) with luminosity levels off for the brightest elliptical galaxies.