Resolving Stellar Populations outside the Local Group: MAD observations of UKS2323-326

TL;DR

This study uses advanced adaptive optics imaging to analyze stellar populations in a dwarf galaxy, providing insights into its star formation history and demonstrating the capabilities of the MAD instrument at ESO VLT.

Contribution

It presents the first deep near-infrared photometry of UKS2323-326 using MAD AO, revealing detailed stellar populations and estimating intermediate-age star formation.

Findings

Detected AGB, red supergiants, and RGB stars down to 1 mag below the RGB tip.

Estimated intermediate-age star formation produced approximately 600,000 solar masses of stars.

Demonstrated the effectiveness of MAD AO for resolving stellar populations in distant galaxies.

Abstract

We present a study aimed at deriving constraints on star formation at intermediate ages from the evolved stellar populations in the dwarf irregular galaxy UKS2323-326. These observations were also intended to demonstrate the scientific capabilities of the multi-conjugated adaptive optics demonstrator (MAD) implemented at the ESO Very Large Telescope as a test-bench of adaptive optics (AO) techniques. We perform accurate, deep photometry of the field using J and Ks band AO images of the central region of the galaxy. The near-infrared (IR) colour-magnitude diagrams clearly show the sequences of asymptotic giant branch (AGB) stars, red supergiants, and red giant branch (RGB) stars down to ~1 mag below the RGB tip. Optical-near-IR diagrams, obtained by combining our data with Hubble Space Telescope observations, provide the best separation of stars in the various evolutionary stages. The counts of AGB stars brighter than the RGB tip allow us to estimate the star formation at intermediate ages. Assuming a Salpeter initial mass function, we find that the star formation episode at intermediate ages produced ~6x10^5 M_sun of stars in the observed region.