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

© 2000 Kluwer Academic Publishers. We thank the referee, Richard de Grijs, for his timely and critical review of this paper. We are grateful to Nicolás Cardiel for his help with the REDucm E package, and to Harold Kuntschner for giving access to his data in electronic form.
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.
Depto. de Física de la Tierra y Astrofísica
Fac. de Ciencias Físicas
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