Larger $\lambda_R$ in the disc of isolated active spiral galaxies than in their non-active twins

Abstract

We present a comparison of the spin parameter $\lambda_R$, measured in a region dominated by the galaxy disc, between 20 pairs of nearby (0.005$<$z$<$0.03) seemingly isolated twin galaxies differing in nuclear activity. We find that 80--82% of the active galaxies show higher values of $\lambda_R$ than their corresponding non-active twin(s), indicating larger rotational support in the AGN discs. This result is driven by the 11 pairs of unbarred galaxies, for which 100% of the AGN show larger $\lambda_R$ than their twins. These results can be explained by a more efficient angular momentum transfer from the inflowing gas to the disc baryonic matter in the case of the active galaxies. This gas inflow could have been induced by disc or bar instabilities, although we cannot rule out minor mergers if these are prevalent in our active galaxies. This result represents the first evidence of galaxy-scale differences between the dynamics of active and non-active isolated spiral galaxies of intermediate stellar masses (10$^{10}<M_*<10^{11}$ M$_{\odot}$) in the Local Universe.Comment: 11 pages, 7 figures. Accepted for publication in A&A Letter