The impact of bars on the properties of H II regions in the TIMER survey

Abstract

In this study, we perform a comparative analysis of the properties of the H II regions located in different areas of barred galaxies, with the aim of investigating the impact of bars on the physical properties of the ionized gas. Based on integral field spectroscopy data for 17 barred galaxies covering approximately the central 6 × 6 kpc, we detect a total of 2200 H II regions, of which 331 are located within the nuclear disc (also known as circumnuclear regions), 661 in the bar region, and 1208 in the disc. Among the physical properties of the H II regions, we explore the O/H and N/O abundances, Hα luminosity, dust extinction, electron density, and Hα equivalent width. We find clear differences in the properties of the H II regions between the nuclear disc, the bar, and the disc, that could be explained by an enhancement in the molecular gas concentration in the central parts driven by bar-induced gas flows. As this gas is channelled towards the galaxy centre, the most extreme values in the analysed properties are found for the circumnuclear H II regions. Unlike the bar strength, galaxy mass does seem to affect the properties of the H II regions, with massive galaxies presenting higher values in most of the properties, possibly due to the increased amount of gas in these systems. This study provides evidence that the bar-driven redistribution of material within the galaxy inner parts causes significant differences in the H II region properties depending on their location within the galaxies.