Upper limits on the mass of supermassive black holes from HST/STIS archival data

The growth of supermassive black holes (SBHs) appears to be closely linked with the formation of spheroids. From the observational point of view there is a pressing need to acquire better statistics on SBH masses since the existing samples are preferentially weighted toward early-type galaxies with very massive SBHs. With this motivation we started a project aimed at measuring upper limits of the mass of the SBHs that can be present in the centers of all the nearby galaxies (D<100 Mpc) for which STIS/G750M spectra are available in the HST archive. These upper limits will be derived from the modeling of the central emission-line widths ([NII]6548,6583AA , Halpha, and [SII]6716,6730AA) observed over an aperture of about 0.1 arcsec (R<50 pc). In this poster we present our preliminary results about a subsample of 20 bulges of early-type disk galaxies (S0--Sb) within 20 Mpc.