Spatially Resolved Metallicity and Ionization Mapping with the SAMI Galaxy Survey

Authors: Henry Poetrodjojo, Brent Groves, Lisa Kewley, others...

Background: The gas-phase metallicity of a galaxy provides an insight into its formation history. Many studies have shown that isolated spiral galaxies have a negative metallicty gradient that is independent of mass or luminosity (Sanchez et al. (2012,2014); Ho et al. 2015; Sanchez-Menguiano 2016). Interacting galaxy pairs tend to have shallower gradients caused by pristine gas inflows and gravitational interactions (Kewley et al. 2010; Rupke et al. 2010; Rich et al. 2012). Many metallicity diagnostics have a dependence on ionization parameter (eg. N2HA, O3N2, R23), with ionization parameter diagnostics also being a function of metallicity. This makes it difficult to determine either property individually.

Project: In this SAMI project, we will produce self-consistent metallicity and ionization parameter maps of star-forming face-on spiral galaxies that fill the majority of the SAMI FOV. Using the iterative method described in Kewley & Dopita 2002, we will account for the interdependence between metallicity and ionization parameter diagnostics. We will analyze the metallicity gradients and the distribution of ionization parameter. From our ionization parameter maps and models presented in Kewley et al. (Submitted), we will analyze how the exclusion of ionization parameter will affect the popular O3N2 metallicity diagnostic (Pettini & Pagel 2004).

This project represents the first part of the larger SAMI project: "Metallicity Gradients as a function of environment" ( Many SAMI galaxies lack the S/N in necessary emission lines (eg. [OII]) to reliably determine the metallicity and ionization parameter. To expand this to the entire SAMI sample, we need to use binning (Radial and Voronoi) to increase the detection of these important lines.

We expect to submit this to the SAMI team for review within the next two weeks

Publication Date: 
December 2017
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