2022MNRAS.509.6183C

We describe the observations of the low metallicity nearby galaxy AGC 198691 (Leoncino Dwarf) obtained with the Integral Field Unit of the instrument MEGARA at the Gran Telescopio Canarias. The observations cover the wavelength ranges 4304-5198 Å and 6098-7306 Å with a resolving power R ≃ 6000. We present 2D maps of the ionized gas, deriving the extension of the H II region and gas kinematics from the observed emission lines. We have not found any evidence of recent gas infall or loss of metals by means of outflows. This result is supported by the closed-box model predictions, consistent with the oxygen abundance found by other authors in this galaxy and points towards Leoncino being a genuine XMD galaxy. We present for the first time spatially resolved spectroscopy allowing the detailed study of a star-forming region. We use POPSTAR + CLOUDY models to simulate the emission-line spectrum. We find that the central emission-line spectrum can be explained by a single young ionizing cluster with an age of ≃ 3.5 ± 0.5 Myr and a stellar mass of ≃ 2 ×10³ M_☉. However, the radial profiles of [ O III] λ 5007Å and the Balmer lines in emission demand photoionization by clusters of different ages between 3.5 and 6.5 Myr that might respond either to the evolution of a single cluster evolving along the cooling time of the nebula (≃ 3 Myr at the metallicity of Leoncino, Z≃ 0.0004) or to mass segregation of the cluster, being both scenarios consistent with the observed equivalent widths of the Balmer lines.