Optimising the analysis of emission lines in galaxies: the case of the MUSE TIMER galaxy NGC 613

TL;DR

This paper presents a detailed analysis of emission lines in the galaxy NGC 613 using MUSE data, developing methods to disentangle complex ionisation mechanisms, gas kinematics, and stellar populations to understand galaxy evolution processes.

Contribution

The study introduces a novel set of steps for modeling multi-component emission lines and characterizing stellar populations in integral field spectroscopy data.

Findings

Evidence of gas inflows along bar dust lanes

Detection of a central biconical outflow aligned with a radio jet

Estimates of electron density, metallicity, and outflow mass rate

Abstract

Galaxy evolution is driven by spatially distributed processes with varying timescales. Integral field spectroscopy provides spatially-resolved information about these processes. Nevertheless, disentangling these processes, which are related to both the underlying stellar populations and the interstellar medium can be challenging. We present a case study on NGC~613, observed with MUSE (Multi-Unit Spectroscopic Explorer) for the TIMER (Time Inference with MUSE in Extragalactic Rings) project, a local barred galaxy, which shows several gas ionisation mechanisms and is rich in both large and inner-scale stellar structures. We develop a set of steps to overcome fundamental problems in the modelling of emission lines with multiple components, together with the characterisation of the stellar populations. That results in the disentanglement of the gas ionisation mechanisms and kinematics, along with an optimal parametrisation for star formation history recovery. Our analysis reveals evidence of gas inflows, which are associated with the bar dust lanes traced with \textit{Hubble} Space Telescope (HST). In addition, we show the gas kinematics in a central biconical outflow, which is aligned with a radio jet observed with Very Large Array (VLA). The emission line provides estimates of electron density, gas-phase metallicity, and the mass outflow rate, allowing us to distinguish intertwined ionisation mechanisms and to identify a part of the multiphase gas cycle in NGC 613. It traces the gas kinematics from the bar lanes to inner scale gas reservoirs, where it can eventually trigger star formation or AGN activity, as observed in the outflow.