A Study on the Evolution of NGC6822. I. Investigating the Star Formation History through Evolved Stellar Populations
Abstract
NGC6822 is an isolated dwarf irregular galaxy in the Local Group at a distance of ∼ 490 kpc . In this paper, we derived the star formation history (SFH) of NGC6822 employing a method based on evolved asymptotic giant branch (AGB) stars, known as long-period variable (LPV) stars. We utilized a dataset of 329 LPVs in JHKs bands to estimate the star formation rate (SFR) over time and reconstructed the SFH of the galaxy. In addition to obtaining the SFH assuming constant metallicity values within the range of 0.0001 < Z < 0.012, we also adopted three distinct age-metallicity relations (AMRs) to account for variations in the chemical content of the galaxy throughout its lifetime. The SFH has been investigated in two regions. The bar region encloses a central area of 189 arcmin2, and the outer region encircles a field beyond the bar region, extending to the radial distance of 3 kpc. In the bar region, we identified three episodes of star formation peaking at t ∼ 4.7 Gyr (log t = 9.67), t ∼ 1.6 Gyr (log t = 9.21), and t ∼ 48 Myr (log t = 7.63), where t is the look-back time. In the outer region, we found one episode of star formation occurring at t ∼ 4.6 Gyr. The significant peak observed ∼ 4-5 Gyr ago further supports the hypothesis suggested by the previous research, indicating that NGC6822 passed through the virial radius of the Milky Way in the past.
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BibTeX
@misc{khatamsaz2026study,
title = {{A Study on the Evolution of NGC6822. I. Investigating the Star Formation History through Evolved Stellar Populations}},
author = {Fatemeh Khatamsaz and Mahdi Abdollahi and Atefeh Javadi and Hamidreza Mahani and Jacco Th. van Loon and Hedieh Abdollahi and Sepideh Ghaziasgar},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.34329},
eprint = {2609.34329},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.34329},
}
RIS
TY - UNPB
TI - A Study on the Evolution of NGC6822. I. Investigating the Star Formation History through Evolved Stellar Populations
AU - Fatemeh Khatamsaz
AU - Mahdi Abdollahi
AU - Atefeh Javadi
AU - Hamidreza Mahani
AU - Jacco Th. van Loon
AU - Hedieh Abdollahi
AU - Sepideh Ghaziasgar
PY - 2026
DA - 2026/09/28
PB - arXiv
DO - 10.48550/arxiv.2609.34329
UR - https://arxiv.org/abs/2609.34329
AB - NGC6822 is an isolated dwarf irregular galaxy in the Local Group at a distance of ∼ 490 kpc . In this paper, we derived the star formation history (SFH) of NGC6822 employing a method based on evolved asymptotic giant branch (AGB) stars, known as long-period variable (LPV) stars. We utilized a dataset of 329 LPVs in JHK_s bands to estimate the star formation rate (SFR) over time and reconstructed the SFH of the galaxy. In addition to obtaining the SFH assuming constant metallicity values within the range of 0.0001 < Z < 0.012, we also adopted three distinct age-metallicity relations (AMRs) to account for variations in the chemical content of the galaxy throughout its lifetime. The SFH has been investigated in two regions. The bar region encloses a central area of 189 arcmin^2, and the outer region encircles a field beyond the bar region, extending to the radial distance of 3 kpc. In the bar region, we identified three episodes of star formation peaking at t ∼ 4.7 Gyr (log t = 9.67), t ∼ 1.6 Gyr (log t = 9.21), and t ∼ 48 Myr (log t = 7.63), where t is the look-back time. In the outer region, we found one episode of star formation occurring at t ∼ 4.6 Gyr. The significant peak observed ∼ 4-5 Gyr ago further supports the hypothesis suggested by the previous research, indicating that NGC6822 passed through the virial radius of the Milky Way in the past.
ER -