I use the metal content of galaxies as probes for their formation histories. Combining analytical chemical evolution models and observations, I am able to verify how different physical conditions affect galaxy formation.
Why the metallicity depends on environment?
The gas-phase metallicity of star-forming galaxies is environmental-dependent. At fixed stellar mass, galaxies located at denser region in the Universe have on average more metal in the gas form. We model the shape of the mass-metallicity relation of galaxies in different density regions and conclude that the gas content in galaxies is the main reason. Galaxies at high density regions contain less gas, therefore, higher metallicity.
Why the metallicity depends on the surface brightness of galaxies?
The metal content in disk galaxies is affected by the surface brightness. Low surface brightness galaxies on average have lower metal content. The surface brightness profile and metallicity gradient of galaxies provide constraint on the history of gas flows going in and out of galaxies. We model the effect of gas flow on the metallicity gradient of galaxies. We conclude that the low metallicity in low surface brightness galaxies is mainly due to their low star-formation efficiency. Inflowing gas does not form stars, therefore, dilute the metallicity.