Insights on the stellar mass-metallicity relation from the CALIFA survey

TL;DR

This study uses CALIFA survey data to analyze how stellar metallicity relates to both local surface density and total stellar mass across different galaxy types, revealing the interplay of local and global factors in galaxy evolution.

Contribution

It provides a detailed comparison of the stellar mass-metallicity relation and local surface density effects across spheroidal and disk galaxies, highlighting the varying influence of local and global processes.

Findings

The stellar mass-metallicity relation (MZR) spans 10^9 to 10^12 M_sun.

Local surface density strongly correlates with stellar metallicity (μZR).

In disks, local density dominates; in spheroids, total mass is more influential.

Abstract

We use spatially and temporally resolved maps of stellar population properties of 300 galaxies from the CALIFA integral field survey to investigate how the stellar metallicity (Z*) relates to the total stellar mass (M*) and the local mass surface density ($\mu$*) in both spheroidal and disk dominated galaxies. The galaxies are shown to follow a clear stellar mass-metallicity relation (MZR) over the whole 10$^9$ to 10$^{12}$ M$_{\odot}$ range. This relation is steeper than the one derived from nebular abundances, which is similar to the flatter stellar MZR derived when we consider only young stars. We also find a strong relation between the local values of $\mu$* and Z* (the $\mu$ZR), betraying the influence of local factors in determining Z*. This shows that both local ($\mu$*-driven) and global (M*-driven) processes are important in determining the metallicity in galaxies. We find that the overall balance between local and global effects varies with the location within a galaxy. In disks, $\mu$* regulates Z*, producing a strong $\mu$ZR whose amplitude is modulated by M*. In spheroids it is M* who dominates the physics of star formation and chemical enrichment, with $\mu$* playing a minor, secondary role. These findings agree with our previous analysis of the star formation histories of CALIFA galaxies, which showed that mean stellar ages are mainly governed by surface density in galaxy disks and by total mass in spheroids.