The EDGE-CALIFA Survey: Influence of Mergers on Radial Profiles of Gas-Phase Metallicity

Abstract

Galaxy mergers are expected to strongly reshape the internal properties of galaxies. However, their impact on chemical enrichment and star formation at different galactocentric radii remains poorly understood. In this study, we investigate how the merger process affects the radial distribution of gas-phase metallicity (oxygen abundance, O/H) and specific star formation rate (sSFR). We analyse 98 galaxies from the EDGE-CALIFA survey, including 49 isolated (non-interacting) and 49 galaxies in four different merger stages (pre-merger, merging, post-merger, and remnant). Analysing the relationship between O/H and sSFR, we find that although it appears that the control galaxies show a weak anti-correlation, it disappears as we probe different merger stages. This lack of a strong physical anti-correlation suggests that merger-induced star formation is not strictly fueled by metal-poor gas inflows. We show that, in comparison with the isolated sample, the pre-merger galaxies show similar metallicity to isolated galaxies. Nevertheless, for the merging galaxies, we note central metal dilution and enhanced star formation with an opposite trend at their outskirts, i.e., chemical enrichment and suppressed star formation. The post-merger galaxies show metallicity dilution for all galactocentric radii. The merger remnant galaxies exhibit slightly enriched metallicity for intermediate regions. In general, O/H profiles vary with radius and merger stage regardless of the molecular gas content. Our results suggest that the chemical evolution in merging galaxies is driven by gas mixing efficiency and the original chemistry of the progenitor galaxies, which is not necessarily metal-poor.