Abstract
ABSTRACT Bars inhabit the majority of local-Universe disc galaxies and may be important drivers of galaxy evolution through the redistribution of gas and angular momentum within discs. We investigate the star formation and gas properties of bars in galaxies spanning a wide range of masses, environments, and star formation rates using the Mapping Nearby Galaxies at APO galaxy survey. Using a robustly defined sample of 684 barred galaxies, we find that fractional (or scaled) bar length correlates with the host’s offset from the star formation main sequence. Considering the morphology of the Hα emission we separate barred galaxies into different categories, including barred, ringed, and central configurations, together with Hα detected at the ends of a bar. We find that only low-mass galaxies host star formation along their bars, and that this is located predominantly at the leading edge of the bar itself. Our results are supported by recent simulations of massive galaxies, which show that the position of star formation within a bar is regulated by a combination of shear forces, turbulence, and gas flows. We conclude that the physical properties of a bar are mostly governed by the existing stellar mass of the host galaxy, but that they also play an important role in the galaxy’s ongoing star formation.
Highlights
Bars inhabit most disk galaxies in the present-day Universe
We investigate the star formation and gas properties of bars in galaxies spanning a wide range of masses, environments, and star formation rates using the Mapping Nearby Galaxies at APO (MaNGA) galaxy survey
We conclude the dominant ionisation mechanism of gas within bars is star formation. This result agrees with previous studies of spatially resolved star formation in barred galaxies, showing that the star formation rate (SFR) of barred galaxies may be enhanced in the centre by the presence of a bar. i.e. the Hα emission is star-forming, not active galactic nuclei (AGN) or line region (LINER)-dominated (Catalan-Torrecilla et al 2017)
Summary
Bars inhabit most disk galaxies in the present-day Universe (e.g. de Vaucouleurs 1963; Eskridge et al 2000; Knapen et al 2000; Nair & Abraham 2010; Masters et al 2011). Ho et al 1997; Coelho & Gadotti 2011), feed the central black hole (Shlosman et al 1989; Jogee 2006), or build up the central mass concentration (Kormendy & Kennicutt 2004) It is not clear whether the presence of a bar is the main driver for rapid gas consumption, but this evidence suggests that bars are at least strongly linked with this process. Ionised gas flow along a bar is even rarer, though previous studies of small samples of galaxies have observed the streaming of [NII] and Hα (e.g. de Vaucouleurs & de Vaucouleurs 1963; Zurita et al 2004; Pan et al 2015) This ionised gas flow is the smoking gun of star formation occurring within bars.
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