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 to elliptical galaxies or to rapidly-rotating, flattened systems more nearly resembling the products of disk internal transformations, are highlighted. The analysis of surface brightness profiles derived from HST data is reviewed to show that unresolved nuclear components detected by HST have biased the determination of surface brightness profiles obtained from the ground; r^1/4 profiles are virtually nonexistent in galaxy bulges. Predictions from accretion N-body models on the shape of surface brightness profiles are discussed. The position of bulges on the Fundamental Plane of elliptical galaxies is examined to infer clues on bulge population ages and bulge dynamical structure. Kinematic diagnostics on the internal dynamics of bulges are examined. Finally, a new approach to the kinematic analysis of galaxies, based on the use of synthetic spectra of single stellar population models instead of the standard stellar templates, is presented.