The AGB population in IC 1613 using JHK photometry

TL;DR

This study uses JHK photometry to analyze the AGB stars in IC 1613, determining its metallicity, spatial distribution, and AGB population characteristics, revealing a consistent metallicity and AGB extent across the galaxy.

Contribution

It provides the first detailed spatial and metallicity analysis of the AGB population in IC 1613 using high-quality JHK photometry.

Findings

The TRGB magnitude is at K_0 = 18.25 +/- 0.15 mag.

The C/M ratio is 0.52 +/- 0.04, indicating a metallicity of [Fe/H] = -1.26 +/- 0.07 dex.

The AGB population extends out to 4.5 kpc without significant metallicity variation.

Abstract

A member of the Local Group, IC 1613 is a gas rich irregular dwarf galaxy that appears to have formed stars continuously over the last 10 Gyr and is relatively independent of external influences from other galaxies. This paper aims to study the spatial distribution of the asymptotic giant branch (AGB) population in IC 1613 and its metallicity. Using WFCAM on UKIRT, high quality JHK photometry of an area of 0.8 deg^2 centered on IC 1613 was obtained. The data have been used to isolate the C- and M-type components of the AGB population and using their number ratio, C/M, a global mean metallicity has been derived. The metallicity and the TRGB magnitude have been studied as a function of distance from the galactic centre and as a function of azimuthal angle. The tip of the RGB (TRGB) has been found at K_0 = 18.25 +/- 0.15 mag. The colour separation between the C- and M-type components of the AGB population has been located at (J-K) = 1.15 +/- 0.05 mag, giving a global C/M ratio of 0.52 +/- 0.04 and from this an iron abundance of [Fe/H] = -1.26 +/- 0.07 dex has been calculated. The AGB population has been detected out to a radial distance of 4.5 kpc in the de-projected plane of the galaxy. The measured TRGB is consistent with previous measurements and no significant variation is detected in the TRGB or in metallicity either with galactocentric distance or azimuthal angle.