Line strengths and line strength gradients in bulges along the Hubble sequence

Abstract

We present first results of a comprehensive survey of deep long-slit spectra along the minor axis of bulges of edge-on spiral galaxies. Our results indicate that stellar populations in bulges are fairly old and encompass a range of metallicities. The luminosity-weighted ages of bulges range from those found for cluster ellipticals to slightly 'younger' (by up to only a few Gyr, however). Their alpha/Fe element ratio is typically supersolar, consistent with those found in giant ellipticals. The radial line-strength gradients in bulges correlate with bulge luminosity. Generally, these findings are more compatible with predictions of the 'dissipative collapse' model than with those of the 'secular evolution' model.