February 4, 1999 CfA Colloquium

Title: Spiral Galaxies with HST: Clues to Bulge Formation

Speaker: C. Marcella Carollo

Abstract: Bulges are a defining component of the entire Hubble sequence; their formation/evolution is a fundamental step in the complex process of `galaxy formation'. The global properties of Sb to Sc bulges challenge the orthodox view that `spheroids' as a family are universally `old' stellar systems, i.e. relics of the early universe, and suggest that `bulge formation' may be an on-going process driven by secular evolution of the disks. A crucial test for the evolutionary scenario is provided by the nuclear, i.e. ~10-100pc scale properties of spheroids along their luminosity sequence. I present the results of a multicolor WFPC2 (V) and NICMOS (H, J) HST survey of the nuclei of ~100 Sa to Sc galaxies, discuss their implications for scenarios of bulge formation, and emphasize new important questions raised by probing the bulges on these - previously unexplored - scales.

Reference for students:
Wyse, Gilmore & Franx, ARA&A, 1997, 35, 637