An Integral Field Study of Abundance Gradients in Nearby LIRGs

TL;DR

This study uses integral field spectroscopy to map metallicity gradients in nearby LIRGs, revealing how mergers flatten these gradients and aligning observations with recent galaxy merger models and simulations.

Contribution

First to generate metallicity maps of LIRGs using WiFeS data, linking abundance gradients to merger stages and validating new theoretical models.

Findings

Metallicity gradients flatten as galaxy mergers progress.

Observed gradients agree with recent merger simulations.

Metal distribution traces gas flows during mergers.

Abstract

We present for the first time metallicity maps generated using data from the Wide Field Spectrograph (WiFeS) on the ANU 2.3m of 9 Luminous Infrared Galaxies (LIRGs) and discuss the abundance gradients and distribution of metals in these systems. We have carried out optical integral field spectroscopy (IFS) of several several LIRGs in various merger phases to investigate the merger process. In a major merger of two spiral galaxies with preexisting disk abundance gradients, the changing distribution of metals can be used as a tracer of gas flows in the merging system as low metallicity gas is transported from the outskirts of each galaxy to their nuclei. We employ this fact to probe merger properties by using the emission lines in our IFS data to calculate the gas-phase metallicity in each system. We create abundance maps and subsequently derive a metallicity gradient from each map. We compare our measured gradients to merger stage as well as several possible tracers of merger progress and observed nuclear abundances. We discuss our work in the context of previous abundance gradient observations and compare our results to new galaxy merger models which trace metallicity gradient. Our results agree with the observed flattening of metallicity gradients as a merger progresses. We compare our results with new theoretical predictions that include chemical enrichment. Our data show remarkable agreement with these simulations.