Bimodal abundance pattern in M51: evidence for corotation resonance effects

TL;DR

This study develops a chemical evolution model for M51, revealing a bimodal abundance pattern influenced by spiral arms and corotation resonance, indicating complex galactic chemical processes.

Contribution

It introduces a new model explaining the bimodal abundance distribution in M51 based on HST data and resonance effects, extending understanding of galactic chemical evolution.

Findings

Bimodal abundance pattern with a steep gradient and plateau.

Corotation resonance influences the abundance slope change.

Evidence of overabundant gas infall onto M51's disc.

Abstract

A chemical evolution model for the bimodal-like abundance distribution in the external galaxy M51 recently derived on the basis of HST data for more than a half million red supergiants is developed. It is shown that, like in our Galaxy, formation of fine structure of the radial abundance pattern -- a rather steep gradient in the internal part of the disc and a plateau in the middle part -- is due to the influence of the spiral arms, the bend in the slope of the distribution being arose near the corotation resonance. Our model strongly suggests that M51 is surrounded by overabundant gas infalling onto its disc.