Metal production in M33: space and time variations

TL;DR

This study analyzes the metallicity distribution and its evolution in the galaxy M33 using nebular and stellar data, revealing a complex metallicity pattern and a slight temporal change in the metallicity gradient.

Contribution

It provides a detailed analysis of metallicity gradients in M33, incorporating new observations and an updated model to understand their spatial and temporal variations.

Findings

Metallicity distribution in M33 shows a central depression.

The metallicity gradient has a slope of about -0.037 dex/kpc.

The gradient slope has evolved slightly over time.

Abstract

Nearby galaxies are ideal places to study in detail metallicity gradients and their time evolution. We consider chemical abundances of a new sample of \hii\ regions complemented with previous literature data-sets. We compare \hii\ region and PN abundances obtained with a common set of observations taken at MMT. With an updated theoretical model, we follow the time evolution of the baryonic components and chemical abundances in the disk of M33, assuming that the galaxy is accreting gas from an external reservoir. Supported by a uniform sample of nebular spectroscopic observations, we conclude that: {\em i}) the metallicity distribution in M33 is very complex, showing a central depression in metallicity probably due to observational bias; {\em ii}) the metallicity gradient in the disk of M33 has a slope of -0.037$\pm$ 0.009 dex kpc$^{-1}$ in the whole radial range up to $\sim$8 kpc, and -0.044$\pm$ 0.009 dex kpc$^{-1}$ excluding the central kpc; {\em iii}) there is a small evolution of the slope with time from the epoch of PN progenitor formation to the present-time.}