Asymptotic Giant Branch Stars in the Phoenix Dwarf Galaxy

TL;DR

This study uses near-infrared and optical photometry to analyze stellar populations in the Phoenix dwarf galaxy, identifying key AGB stars and estimating its distance and age distribution.

Contribution

It presents new near-infrared photometry data and identifies a Mira variable, providing insights into the galaxy's distance and intermediate-age stellar population.

Findings

Discovery of a Mira variable indicating a ~2 Gyr population

Distance modulus estimated at 23.10±0.18

Identification of carbon and AGB stars related to different populations

Abstract

JHKs near-infrared photometry of stars in the Phoenix dwarf galaxy is presented and discussed. Combining these data with the optical photometry of Massey et al. allows a rather clean separation of field stars from Phoenix members. The discovery of a Mira variable (P = 425 days), which is almost certainly a carbon star, leads to an estimate of the distance modulus of 23.10+/-0.18 that is consistent with other estimates and indicates the existence of a significant population of age ~2 Gyr. The two carbon stars of Da Costa have M{bol} = -3.8 and are consistent with belonging to a population of similar age; some other possible members of such a population are identified. A Da Costa non-carbon star is Delta Ks~0.3 mag brighter than these two carbon stars. It may be an AGB star of the dominant old population. The nature of other stars lying close to it in the Ks,(J-Ks) diagram needs studying.