SDSS-IV MaNGA: Global stellar population and gradients for about 2000 early-type and spiral galaxies on the mass-size plane

TL;DR

This study analyzes stellar populations and kinematics of about 2000 galaxies from MaNGA, revealing how galaxy properties vary systematically along the mass-size plane and differ between early-type and spiral galaxies.

Contribution

It provides a comprehensive analysis of stellar populations and kinematic properties across a large galaxy sample, extending the understanding of the mass plane and gradients for both early-type and spiral galaxies.

Findings

Galaxies lie on a tight mass plane close to virial theorem predictions.

Stellar population properties vary systematically with velocity dispersion.

Metallicity gradients peak around a critical velocity dispersion and differ between galaxy types.

Abstract

We perform full spectrum fitting stellar population analysis and Jeans Anisotropic modelling (JAM) of the stellar kinematics for about 2000 early-type galaxies (ETGs) and spiral galaxies from the MaNGA DR14 sample. Galaxies with different morphologies are found to be located on a remarkably tight mass plane which is close to the prediction of the virial theorem, extending previous results for ETGs. By examining an inclined projection (`the mass-size' plane), we find that spiral and early-type galaxies occupy different regions on the plane, and their stellar population properties (i.e. age, metallicity and stellar mass-to-light ratio) vary systematically along roughly the direction of velocity dispersion, which is a proxy for the bulge fraction. Galaxies with higher velocity dispersions have typically older ages, larger stellar mass-to-light ratios and are more metal rich, which indicates that galaxies increase their bulge fractions as their stellar populations age and become enriched chemically. The age and stellar mass-to-light ratio gradients for low-mass galaxies in our sample tend to be positive ($\rm centre<outer$), while the gradients for most massive galaxies are negative. The metallicity gradients show a clear peak around velocity dispersion $\log_{10} \sigma_{\rm e}\approx 2.0$, which corresponds to the critical mass $\sim 3\times 10^{10}M_{\odot}$ of the break in the mass-size relation. Spiral galaxies with large mass and size have the steepest gradients, while the most massive ETGs, especially above the critical mass $M_{\rm crit}\ge 2\times 10^{11} M_{\odot}$, where slow rotator ETGs start dominating, have much flatter gradients. This may be due to differences in their evolution histories, e.g. mergers.