Title: The stellar mass - metallicity relation for nearby galaxies
　  Speaker: Dr. Thomas Marcus Hughes (Kavli Institute Fellow, KIAA)
　  Time: May 11th, Friday, 2pm
　  Location: middle conference room

Abstract: The observed relationship between stellar mass and metallicity is a useful tool for constraining models of galaxy formation and evolution. However, the mechanisms driving this relation and the role played by the environment, are still not well understood. I will present results from a new study on the role of gas content and environment in shaping this relation, using a magnitude- and volume-limited sample of 260 nearby late-type galaxies in different environments. Combining new estimates of the gas-phase oxygen abundance with ultraviolet to near-infrared photometry and HI 21 cm line observations,  I show that, at fixed stellar mass, galaxies with lower gas fractions typically also possess higher oxygen abundances. We also observe a relationship between gas fraction and metal content, whereby gas-rich galaxies are typically metal-poor. Although some cluster galaxies are gas-deficient objects, statistically the stellar-mass metallicity relation is invariant to the environment, in agreement with recent studies. These results suggest that internal evolutionary processes, rather than environmental effects, play a key role in shaping the stellar mass-metallicity relation.