Program: GN-2006A-Q-77

Because bulges lie in the fundamental plane defined by ellipticals, bulges and ellipticals have been viewed as having followed similar evolutionary paths, albeit in different environments. However, there is evidence which suggests that bulges have evolved secularly from disks to varying degrees, and in this sense chemical properties may be linked. How bulge and disk chemistry compares outside the Milky Way, though, is largely unexplored, owing to a lack of common abundance diagnostics. We propose to carry out spectroscopy of planetary nebulae in the bulge and disk of M81 in order to measure and compare oxygen abundances. Simultaneously, R_23 will be measured for many HII regions in the disk of M81. Besides being relevant to studies of disk-bulge linkages, the bulge measurements will yield quantitative information about gas flows and mass loss up to the time of the supernovae-driven wind, and the disk measurements will enable reliable calibration of the abundance scale for metal-rich HII regions.