SDSS-IV MaNGA: What Shapes The Distribution Of Metals In Galaxies? Exploring The Roles Of The Local Gas Fraction And Escape Velocity

TL;DR

This study analyzes over 900,000 star-forming regions in 1023 galaxies to understand how local metallicity is influenced by gas fraction and escape velocity, highlighting the primary role of gas fraction in chemical enrichment.

Contribution

It demonstrates that local gas fraction is the main factor affecting metallicity and supports a gas-regulator model consistent with momentum-driven outflows.

Findings

Metallicity decreases with higher gas fraction and lower escape velocity.

Gas fraction has a more significant impact on metallicity than escape velocity.

The gas-regulator model explains local metallicity variations effectively.

Abstract

We determine the local metallicity of the ionized gas for more than $9.2\times 10^5$ star forming regions (spaxels) located in 1023 nearby galaxies included in the SDSS-IV MaNGA IFU survey. We use the dust extinction derived from the Balmer decrement and stellar template fitting in each spaxel to estimate the local gas and stellar mass densities, respectively. We also use the measured rotation curves to determine the local escape velocity ($\mathrm{V_{esc}}$). We have then analyze the relationships between the local metallicity and both the local gas fraction ($\mu$) and $\mathrm{V_{esc}}$. We find that metallicity decreases with both increasing $\mu$ and decreasing $\mathrm{V_{esc}}$. By examining the residuals in these relations we show that the gas fraction plays a more primary role in the local chemical enrichment than $\mathrm{V_{esc}}$. We show that the gas-regulator model of chemical evolution provides a reasonable explanation of the metallicity on local scales. The best-fit parameters for this model are consistent with metal loss caused by momentum-driven galactic outflows. We also argue that both the gas fraction and local escape velocity are connected to the local stellar surface density, which in turn is a tracer of the epoch at which the dominant local stellar population formed