Unveiling gas kinematics and stellar populations in H <scp>ii</scp> regions inside the low-metallicity dwarf nearby galaxy SDSSJ0859 + 3923 with MEGARA at the GTC

ABSTRACT In this study, we present Integral Field Unit observations of the galaxy SDSSJ0859 + 3923, utilizing the MEGARA (Multi Espectrógrafo en GTC de Alta Resolución para Astronomía) instrument on the GTC (Gran Telescopio Canarias) 10.4m telescope. These observations were conducted in two distinct spectral ranges: 4332–5222 Å and 6097–7345 Å, with a high resolving power (R$_\mathrm{FWHM}$$\sim 6\, 000$), and spatial resolution of 25 pc, considering the galaxy’s distance of 8.5 Mpc. Our observations have identified five H ii regions, whose precise positions were determined using data from the Wide Field Camera 3 (ultraviolet and visible) of the Hubble Space Telescope, WFC3-UVIS/HST, archive images, where we also detected the associated blue underlying continuum linked to the ionized knots. A detailed kinematic analysis of these regions revealed low-velocity dispersion values (around 10 km s$^{-1}$) in four H ii regions, indicating a lack of significant turbulent events. In the fifth region, we observed a peak in velocity dispersion reaching 40 km s$^{-1}$, which we interpret as the result of hot star winds and/or a recent type-II supernova explosion. We have conducted a comprehensive spectral analysis of the H ii regions, obtaining emission-line fluxes that enabled us to confirm the oxygen abundance (12 + log(O/H) = 7.41 $\pm$ 0.15) and, using popstar models, to constrain the age and mass of the ionizing young clusters.