Spheroid and disk signatures in galaxy bulges^*

Abstract

Recent progress on the structure and dynamics of bulges is reviewed.Those aspects that link galaxy bulges either to oblate spheroids akin toelliptical galaxies or to rapidly-rotating, flattened systems more nearlyresembling the products of disk internal transformations, are highlighted. Theanalysis of surface brightness profiles derived from HST data is reviewed toshow that unresolved nuclear components detected by HST have biased thedetermination of surface brightness profiles obtained from the ground; r^1/4 profiles are virtually nonexistent in galaxybulges. Predictions from accretion N-body models on the shape of surfacebrightness profiles are discussed. The position of bulges on the FundamentalPlane (FP) of elliptical galaxies is examined to infer clues on bulgepopulation ages and bulge dynamical structure. Kinematic diagnostics on theinternal dynamics of bulges are examined. Finally, a new approach to thekinematic analysis of galaxies, based on the use of synthetic spectra of singlestellar population models instead of the standard stellar templates, ispresented.