Bars in the local universe: The PHANGS perspective

Galaxies in the local universe display a wide range of stellar structures, among which bars often stand out. In this talk, I introduce the PHANGS project in some detail and present a set of masks that delimit morphological environments. Then, I move on to highlight some results on the distribution of gas and star formation within bars in PHANGS. Bars contain large amounts of molecular gas and star formation, with average surface densities comparable to those in spiral arms. Yet, there is significant diversity among bars, with some showing more gas and star formation than others; the distribution within bars is also far from symmetric. Molecular gas surface density tends to be slightly higher in bar ends than within the rest of the bar (excluding centres), and the star formation rate surface density is comparatively even higher. The resulting star formation efficiency is typically 2-3 times higher in bars ends than within the bar (excluding centres). The highest surface densities are reached in the centres of barred galaxies, which are systematically brighter than unbarred galaxy centres, and with a distribution that shows a much larger scatter. This could be related to local conditions that are highly variable over time in the centres of barred galaxies as the result of episodic gas inflow.