Dust at sub-solar metallicity: the case of post-AGB stars in the Large Magellanic Cloud

TL;DR

This study examines how sub-solar metallicity influences dust composition in post-AGB stars in the Large Magellanic Cloud, revealing unique dust features and differences from Galactic counterparts.

Contribution

It provides new insights into dust formation at low metallicity by analyzing mid-infrared spectra of post-AGB stars in the LMC, highlighting differences from Galactic stars.

Findings

Detection of rare dust features like the 21 micron feature in LMC stars

Presence of PAH features similar to Galactic stars in some LMC objects

Identification of a unique 7.85 micron feature not seen in Galactic post-AGB stars

Abstract

Low- and intermediate-mass stars are one of the important dust sources in the interstellar medium (ISM) of galaxies. The compositions of dust ejected from these stars are likely to affect those in the ISM. We investigate dust in post-Asymptotic Giant Branch (AGB) stars, which are in a late evolutionary phase for low- and intermediate-mass stars, and which produce a wide variety of dust grains. We are particularly targeting post-AGB stars in the Large Magellanic Cloud (LMC), which has about half of the solar metallicity, to investigate the effects of sub-solar metallicity on dust compositions. Using the Spitzer Space Telescope, we obtained 5-30 micron spectra of 24 post-AGB candidates in the LMC. Five are C-rich post-AGB stars, and this presentation focuses on spectra of these stars. We found that rare dust features in the Milky Way, such as a 21 micron unidentified feature are commonly found in LMC post-AGB stars. The 6-8 micron spectra are compared with those of Galactic objects. Four spectra match the Galactic templates of polycyclic aromatic hydrocarbon (PAH) features. However, we found the three objects show 7.85 micron feature which have not found in Galactic post-AGB stars. Low metallicity conditions definitely affect the dust formation process and compositions.