The AGB population of NGC 6822

TL;DR

This study investigates the distribution and metallicity gradient of asymptotic giant branch stars in NGC 6822 using near-infrared photometry, revealing spatial variations in stellar composition and metallicity.

Contribution

It provides the first detailed analysis of AGB star populations and metallicity distribution in NGC 6822 through near-infrared data and C/M ratio analysis.

Findings

Mean C/M ratio of 0.288 +/- 0.014

Corresponding [Fe/H] = -1.14 +/- 0.08 dex

Detected variations in metallicity and tip of red giant branch with galactic radius

Abstract

The metallicity gradient and the stellar distribution within the Local Group dwarf galaxy NGC 6822 has been studied photometrically using asymptotic branch stars (AGB). In order to study the stellar and metallicity distribution, the carbon- and oxygen-rich AGB stars have been isolated using deep high-quality near-infrared UKIRT photometry. The ratio between them, the C/M ratio, has been used to derive the [Fe/H] abundance within the galaxy. The [Fe/H] abundance and stellar distribution were analysed as a function of galactic radius. A mean C/M ratio of 0.288 +/- 0.014 has been found which corresponds to an iron abundance of [Fe/H] =-1.14 +/-0.08 dex, with variations in the north and south, as well as at larger galactocentric distances. Variations in the magnitude of the tip of the red giant branch has also been detected.