A new galactic chemical evolution model with dust: results for dwarf irregular galaxies and DLA systems

TL;DR

This paper introduces a comprehensive galactic chemical evolution model incorporating dust processes, successfully explaining observed dust and abundance patterns in dwarf irregular galaxies and DLA systems, highlighting the importance of dust accretion and iron dust sources.

Contribution

The model includes updated dust cycle prescriptions and applies to dwarf irregulars and DLA systems, providing new insights into dust formation, destruction, and accretion processes.

Findings

Reproduces observed gas to dust ratios in dwarf galaxies.

Dust accretion is a key process, often dominant in dust evolution.

Iron depletion patterns suggest additional iron dust sources like Type Ia SNe.

Abstract

We present a galactic chemical evolution model which adopts updated prescriptions for all the main processes governing the dust cycle. We follow in detail the evolution of the abundances of several chemical species (C, O, S, Si, Fe and Zn) in the gas and dust of a typical dwarf irregular galaxy. The dwarf irregular galaxy is assumed to evolve with a low but continuous level of star formation and experience galactic winds triggered by supernova explosions. We predict the evolution of the gas to dust ratio in such a galaxy and discuss critically the main processes involving dust, such as dust production by AGB stars and Type II SNe, destruction and accretion (gas condensation in clouds). We then apply our model to Damped Lyman-Alpha systems which are believed to be dwarf irregulars, as witnessed by their abundance patterns. Our main conclusions are: i) we can reproduce the observed gas to dust ratio in dwarf galaxies. ii) We find that the process of dust accretion plays a fundamental role in the evolution of dust and in certain cases it becomes the dominant process in the dust cycle. On the other hand, dust destruction seems to be a negligible process in irregulars. iii) Concerning Damped Lyman-Alpha systems, we show that the observed gas-phase abundances of silicon, normalized to volatile elements (zinc and sulfur), are in agreement with our model. iv) The abundances of iron and silicon in DLA systems suggest that the two elements undergo a different history of dust formation and evolution. Our work casts light on the nature of iron-rich dust: the observed depletion pattern of iron is well reproduced only when an additional source of iron dust is considered. Here we explore the possibility of a contribution from Type Ia SNe as well as an efficient accretion of iron nano-particles.