Dust production from sub-solar to super-solar metallicity in Thermally Pulsing Asymptotic Giant Branch Stars

TL;DR

This study models dust production in TP-AGB stars across various metallicities, revealing insights into silicate formation, dust destruction mechanisms, and the impact on interstellar medium enrichment, with implications for galaxy evolution.

Contribution

It provides new models of dust chemistry and growth in TP-AGB stars at different metallicities, challenging previous assumptions about dust-to-gas ratios and destruction processes.

Findings

Silicate production in M-stars is affected by chemisputtering efficiency.

Total dust ejecta are less dependent on metallicity than previously thought.

Results inform understanding of dust enrichment in galaxies across cosmic time.

Abstract

We discuss the dust chemistry and growth in the circumstellar envelopes (CSEs) of Thermally Pulsing Asymptotic Giant Branch (TP-AGB) star models computed with the COLIBRI code, at varying initial mass and metallicity (Z=0.001, 0.008, 0.02, 0.04, 0.06). A relevant result of our analysis deals with the silicate production in M-stars. We show that, in order to reproduce the observed trend between terminal velocities and mass-loss rates in Galactic M-giants, one has to significantly reduce the efficiency of chemisputtering by H2 molecules, usually considered as the most effective dust destruction mechanism. This indication is also in agreement with the most recent laboratory results, which show that silicates may condense already at T=1400 K, instead than at Tcond=1000 K, as obtained by models that include chemisputtering. From the analysis of the total dust ejecta, we find that the total dust-to-gas ejecta of intermediate-mass stars are much less dependent on metallicity than usually assumed. In a broader context, our results are suitable to study the dust enrichment of the interstellar medium provided by TP-AGB stars in both nearby and high redshift galaxies.