Beyond BPT: A New Multi-Dimensional Diagnostic Diagram for Classifying Power Sources in Galaxy Surveys

The current methods of identifying the ionizing source of warm gas are well defined for the era of single fiber spectroscopy, but integral field spectroscopy has shown that galaxies are complex. The old 2D strong emission line diagnostic diagrams struggle to distinguish shocks from AGN and do not make full use of the now-common rich spatially resolved dataset. We propose a new method of separating gas ionized by star formation, shocks, and AGN by use of a multi-dimensional diagnostic diagram. This new method is tested and analyzed using the SAMI Galaxy Survey Data Release 3 which contains 3068 nearby galaxies. We find an approximately 20% increase in the number of galaxies with shock and AGN signatures as opposed to using only emission line diagnostics. This includes galaxies with low-powered AGN as well as low velocity shocks that are undetected with previous methods. There are also nearly 300 galaxies detected that have elevated emission line ratios, but kinematics that are not associated with feedback from an AGN or regions of shocked gas. We present common characteristics of these unusual galaxies and plan to further investigate them. The results of our analysis and new classifications will be released in the form of shock maps for the SAMI survey. These data products will show the percentage contribution of each ionizing source on a per pixel basis for each galaxy.