Abstract
Characterizing the variation of abundances across a galaxy can improve our understanding of turbulence, gas flows, and the impact of feedback on a galaxy's chemical evolution. Direct abundance measurements require constraints on electron temperature, Te, and a variety of recent observations have revealed systematic variations in Te measured from ions in different HII region ionization zones. We present direct Oxygen, Nitrogen, and Sulfur abundances, measured using Te from the optical auroral lines ([NII]?5756, [OII]??7320,7330, [SII]??4069,4076, [OIII]?4363, and [SIII]?6312) for a sample of HII regions in seven nearby galaxies. The sample galaxies come from Physics at High Angular resolution in Nearby Galaxies survey (PHANGS) and were observed using integral field spectrographs on Keck (Keck Cosmic Web Imager; KWCI) and the Very Large Telescope (Multi-Unit Spectroscopic Explorer; MUSE). To investigate possible sources of Te variation, we compare the differences between our measured Te from the 5 ions with HII region and interstellar medium environmental properties such as ionization parameter, CO velocity dispersion, stellar mass, and stellar ages (obtained from PHANGS-ALMA and PHANGS-HST observations). We find that the temperatures from [OII] and [SII] auroral lines are likely over-estimated due to the presence of electron density inhomogeneities. We measure high [OIII] temperatures in a subset of regions with high CO velocity dispersion and low ionization parameter that may be explained by the presence of low-velocity shocks. We also find that the [NII] and [SIII] temperatures are in good agreement and that the temperatures are minimally impacted by ISM and stellar properties
