Iranian Journal of Physics Research

Calculation of Dust Production by Long-Period Variable Stars in the Galaxy NGC 6822‎

Document Type : Original Article

Authors

Hamidreza Mahani 1
Atefeh Javadi 1
Hedieh Abdollahi 2
Fatemeh Khatamsaz 1

1 School of Astronomy, Institute for Research in Fundamental Sciences (IPM), Tehran, 19568-36613, Iran

2 School of Astronomy, Institute for Research in Fundamental Sciences (IPM), Tehran, 19568-36613, Iran and Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences, MTA Centre of Excellence, Konkoly-Thege Mikl ́ośut 15-17, H-1121, Budapest, Hungary

https://doi.org/10.47176/ijpr.26.2.62122
Abstract
Mass loss from evolved stars, particularly long-period variable stars (LPVs), plays a critical role in enriching the interstellar medium and contributing to galactic evolution. This study investigates the mass-loss rates of LPVs in the irregular dwarf galaxy NGC 6822 using infrared data from ground-based telescopes in the wavelength range of 1.2 to 2.2 micrometers and data from the Spitzer Space Telescope at 3.6 and 4.5 micrometers. By deriving the spectral energy distributions of these stars and analyzing their radiative properties, the overall mass-loss rates of carbon-rich and oxygen-rich stars were determined. The results indicate a total mass-loss rate from LPVs of approximately 2.7 × 10⁻⁵ M☉ yr⁻¹, with dust production contributing roughly 3.7 × 10⁻⁹ M☉ yr⁻¹, while the remainder is attributed to ejected gas. Furthermore, oxygen-rich and carbon-rich stars contribute 22% and 78%, respectively, to the total mass loss of LPVs. Given the low metallicity of this galaxy, the dominant role of carbon-rich stars in the production of interstellar dust is expected. Considering the estimated current star formation rate in the bar region of NGC 6822, reported as 1.7 × 10⁻² M☉ yr⁻¹, the findings suggest that the mass returned by LPVs is insufficient to provide the interstellar material required to sustain ongoing star formation in this galaxy.

Keywords

Evolved stars
Dust
Local Group
Dwarf galaxy
Irregular galaxy
Spectral energy distribution
Subjects
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