GALACTIC BULGES

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Abstract
▪ Abstract We discuss the present observational and theoretical understanding of the stellar populations of bulges and their implications for galaxy formation and evolution. The place of bulges as key to the Hubble Sequence remains secure, but some old paradigms are giving way to new ones as observations develop. Detailed studies of Local Group bulges and haloes provide a basis on which we consider higher redshift data. We present the evidence for and against the currently common preconceptions that bulges are old, above solar metallicity in the mean, and simply scaled-down versions of ellipticals. We conclude life is not so simple: Bulges are diverse and heterogeneous, and although their properties vary systematically, sometimes they are reminiscent of disks, sometimes of ellipticals. The extant observational data are, however, limited. New and future surveys will rectify this, and we discuss the questions those data will address.
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