SDSS-IV MaNGA: stellar rotational support in disc galaxies versus central surface density and stellar population age

We investigate how the stellar rotational support changes as a function of spatially resolved stellar population age (D_n4000) and relative central stellar surface density (ΔΣ₁) for MaNGA isolated/central disc galaxies. We find that the galaxy rotational support indicator λ_Re varies smoothly as a function of ΔΣ1 and D_n4000. D_n4000 versus ΔΣ₁ follows a ‘J-shape’, with λ_Re contributing to the scatters. In this ‘J-shaped’ pattern rotational support increases with central D_n4000 when ΔΣ₁ is low but decreases with ΔΣ₁ when ΔΣ₁ is high. Restricting attention to low-ΔΣ₁ (i.e. large-radius) galaxies, we suggest that the trend of increasing rotational support with D_n4000 for these objects is produced by a mix of two different processes, a primary trend characterized by growth in λ_Re along with mass through gas accretion, on top of which disturbance episodes are overlaid, which reduce rotational support and trigger increased star formation. An additional finding is that star-forming galaxies with low ΔΣ₁ have relatively larger radii than galaxies with higher ΔΣ₁ at fixed stellar mass. Assuming that these relative radii rankings are preserved while galaxies are star forming then implies clear evolutionary paths in central D_n4000 versus ΔΣ₁. The paper closes with comments on the implications that these paths have for the evolution of pseudo-bulges versus classical bulges. The utility of using D_n4000–ΔΣ₁ to study λ_Re reinforces the notion that galaxy kinematics correlate both with structure and with stellar-population state, and indicates the importance of a multidimensional description for understanding bulge and galaxy evolution.