Are High Σ₁ Massive Blue Spiral Galaxies Rejuvenated Systems?

Quiescent galaxies generally possess denser cores than star-forming galaxies with similar mass. As a measurement of the core density, the central stellar mass surface density within a radius of 1 kpc (Σ₁) was thus suggested to be closely related to galaxy quenching. Massive star-forming galaxies with high Σ₁ do not fit into this picture. To understand the origin of such galaxies, we compare the spatially-resolved stellar population and star formation properties of massive (> 1010.5 M_) blue spiral galaxies with high and low Σ₁, divided by Σ₁ = 109.4 M_ \, kpc⁻², based on the final release of MaNGA IFU data. We find that both high Σ₁ and low Σ₁ blue spirals show large diversities in stellar population and star formation properties. Despite the diversities, high Σ₁ blue spirals are statistically different from the low Σ₁ ones. Specifically, the radial profiles of the luminosity-weighted age and Mgb/Fe show that high Σ₁ blue spirals consist of a larger fraction of galaxies with younger and less α-element enhanced centers than their low Σ₁ counterparts, ~ 55% versus ~ 30%. The galaxies with younger centers mostly have higher central specific star formation rates, which still follow the spaxel-based star formation main sequence relation though. Examinations of the Hα velocity field and the optical structures suggest that galactic bars or galaxy interactions should be responsible for the rejuvenation of these galaxies. The remaining ~ 45% of high Σ₁ blue spirals are consistent with the inside-out growth scenario.