The Most Predictive Physical Properties for the Stellar Population Radial Profiles of Nearby Galaxies

Abstract

We present a study on the radial profiles of D4000,luminosity-weighted stellar ages $τ_L$,and luminosity-weighted stellar metallicities $[Z/H]_L$ of 3654 nearby galaxies($0.01<z<0.15$)using the IFU spectroscopic data from the MaNGA survey available in the SDSS DR15,in an effort to explore the connection between median stellar population radial gradients($\nabla$D4000,$\nablaτ_L,\nabla[Z/H]_L$)out to~$1.5R_e$ and various galaxy properties,including stellar mass($M_\star$),specific star formation rate(sSFR),morphologies,and local environment. We find that $M_\star$ is the single most predictive physical property for$\nabla$D4000 and$\nabla[Z/H]_L$. The most predictive properties for $\nablaτ_L$ are sSFR,and to a lesser degree,$M_\star$. The environmental parameters,including local galaxy overdensities and central-satellite division,have virtually no correlation with stellar population radial profiles for the whole sample,but the $\nabla$D4000 of star-forming satellite galaxies with$M_\star\lesssim 10^{10}M_\odot$exhibit a significant positive correlation with galaxy overdensities. Galaxies with lower sSFR have on average steeper negative stellar population gradients,and this sSFR dependence is stronger for more massive star-forming galaxies. The negative correlation between the median stellar population gradients and$M_\star$ are best described largely as segmented relationships, whereby median gradients of galaxies with$\log M_\star\lesssim 10$(with the exact value depending on sSFR)have much weaker mass dependence than galaxies with higher$M_\star$. While the dependence of the radial gradients of ages and metallicities on T-Types and central stellar mass surface densities are generally not significant,galaxies with later T-Types or lower central mass densities tend to have significantly lower D4000,younger$τ_L$ and lower$[Z/H]_L$ across the radial ranges probed in this study.