Revisiting the Mass-Excitation (MEx) diagram using the MaNGA dataset

TL;DR

This study revises the mass-excitation (MEx) diagram using MaNGA integral field spectroscopy, highlighting the importance of Hα equivalent width and the impact of using central versus integrated galaxy properties for ionization classification.

Contribution

It introduces a revised MEx diagram incorporating Hα equivalent width and compares central versus integrated spectral measurements for galaxy ionization analysis.

Findings

Hα equivalent width improves ionization mechanism constraints.

Galaxy position in the MEx diagram varies with spectral measurement type.

Revised diagram enhances classification accuracy for high-redshift galaxies.

Abstract

The diagram comparing the flux ratio of the [OIII] and H$\beta$ 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 between star formation and active galactic nuclear ones. 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 the physical parameters of this diagram, the equivalent width of the H$\alpha$ 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.