Fuelling the central region of galaxies with misaligned gas accretion

ABSTRACT Recent studies have shown that the accretion of kinematically misaligned gas fuels the central reservoir of galaxies, triggering nuclear activity and star formation. In this work, we show that this specific accretion channel can only sustain main–sequence levels of star formation in galaxies with $M_* \lesssim 10^{10}\, {\rm M_\odot }$. Using a sample of 201 kinematically misaligned galaxies, and a comparison sample of 3689 aligned galaxies, from the Mapping Nearby Galaxies at Apache Point Observatory survey, we investigate the impact of kinematically misaligned gas on star formation across stellar mass. We characterize the global specific star formation rate, central concentration and mass of ionized gas of our samples, and derive radial profiles of specific star formation rate and ionized gas mass surface density. We find that misaligned galaxies exhibit more centrally concentrated ionized gas than their aligned counterparts, with the strongest enhancement occurring at intermediate masses ($10^{10}$–$10^{10.6}\, {\rm M_\odot }$), where the central ionized–gas density peaks. In galaxies less massive than $10^{10}\, {\rm M_\odot }$, misaligned gas fuels nuclear star formation at rates typical of star-forming systems. At higher masses, however, the impact of this newly accreted gas is diluted by the larger pre-existing stellar mass in the central regions, limiting its ability to rejuvenate the star formation activity in these galaxies. Our results also show that misaligned galaxies with or without nuclear activity exhibit similar central concentrations of ionized gas, suggesting that most have a reservoir capable of fuelling their supermassive black holes over time-scales longer than typical nuclear activity episodes.