Expanding on the fundamental metallicity relation in dwarf galaxies with MUSE^⋆

¹ European Space Agency (ESA), European Space Exploration and Research Centre (ESTEC), Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
e-mail: teob1823@mit.edu
² Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
³ SRON Netherlands Institute for Space Research, Niels Bohrweg 4, 2333 CA Leiden, The Netherlands
⁴ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
⁵ Department of Astrophysics, University of Vienna, Türkenschanzstrasse 17, 1180 Wien, Austria
⁶ Institute of Physics, Laboratory of Astrophysics, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1290 Sauverny, Switzerland
⁷ Max-Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
⁸ Instituto de Astrofisica de Canarias, 38205 La Laguna, Tenerife, Spain
⁹ Departamento de Astrofısica, Universidad de La Laguna, 38205 La Laguna, Tenerife, Spain

Received: 26 January 2023
Accepted: 13 September 2023

Abstract

The mass–metallicity relation (MZR) represents one of the most important scaling relations in the context of galaxy evolution, comprising a positive correlation between stellar mass and metallicity (Z). The fundamental metallicity relation (FMR) introduces a new parameter into the dependence, namely, the star formation rate (SFR). While several studies have found that Z is anti-correlated with the SFR at a fixed mass, the validity of this statement has been questioned extensively and no widely accepted consensus has been reached thus far. With this work, we investigate the FMR in nine nearby, spatially resolved, dwarf galaxies, using gas diagnostics on integral-field spectroscopic data of the Multi Unit Spectroscopic Explorer (MUSE), pushing such investigations to lower galaxy masses and higher resolutions. We find that both the MZR and FMR exhibit different behaviours within different star-forming regions of the galaxies. We find that the SFR surface-density-and-metallicity anti-correlation is tighter in the low-mass galaxies of our sample. For all the galaxies considered, we find a SFR surface-density-and-stellar-mass surface-density correlation. We propose that the main reason behind these findings is connected to the accretion mechanisms of the gas fuelling star formation, namely: low-mass, metal-poor galaxies accrete pristine gas from the intergalactic medium, while in more massive and metal-enriched systems, the gas responsible for star formation is recycled from previous star-forming episodes.