Revisiting the Mass-excitation (MEx) Diagram using the MaNGA Data Set

Abstract

Abstract The diagram comparing the flux ratio of the [O  iii] and Hβ  emission lines with the total stellar mass of galaxies (also known as the mass-excitation diagram, MEx) has been widely used to classify the ionization mechanism in high redshift galaxies, dividing star-forming galaxies from those where active galactic nuclei are important. This diagram was mainly derived using single-fiber spectroscopy from the SDSS-DR7 survey. In this study, we revise this diagram using the central and integrated spectral measurement from the entire Integral Field Spectroscopic MaNGA sample. Our results suggest that along with these physical parameters, the equivalent width of the Hα  emission line is also required to constrain the ionization mechanism of a high-redshifted galaxy. Furthermore, the location of a galaxy in the excitation-mass diagram varies depending on the use of central or integrated properties.