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Australian Human Resources Institute Diversity Awards 2013 Finalist

Maritza Lara-Lopez (AAO)

"A deeper view of the mass, metallicity, SFR, and HI relationships"

Abstract. *** Note Special Location: NMI Meeting Room 11 (3rd Floor, outside Canteen) ***

We demonstrate that the space formed by the star formation rate (SFR), gas-phase metallicity (Z), and stellar mass can be reduced to a plane. We study three different approaches to find the best representation of this 3D space, using a principal component analysis (PCA), a regression fit, and binning of the data. The PCA shows that this 3D space can be adequately represented in only two dimensions, i.e., a plane. We find that the plane that minimizes the χ2 for all variables, and hence provides the best representation of the data, corresponds to a regression fit to the stellar mass as a function of SFR and Z, Mass= f(Z, SFR). We find that the distribution resulting from the median values in bins for our data gives the highest χ2. The fact that we can represent stellar mass as a linear combination of SFR and metallicity suggests that the stellar mass of a galaxy can be thought of as the rate at which a galaxy is currently forming stars (SFR), plus a measure of the star formation history, here represented by the metallicit, corresponding to the amount of reprocessing of the gas by past stellar generations. The SF history and current SFR of a galaxy are closely linked to the stellar mass.

Finally, using data from SDSS, GAMA, ALFALFA and GASS surveys, we generate a model based on the Z-SSFR relation that shows that at a given stellar mass, depending on the amount of gas, galaxies will follow opposite behaviours.

Held in the Other at 11:00 AM on Thursday, 18 July 2013