Open clusters in the Third Galactic Quadrant. II. The intermediate age open clusters NGC 2425 and NGC 2635

TL;DR

This study analyzes CCD photometric data of two intermediate-age open clusters, NGC 2425 and NGC 2635, revealing their ages, distances, and metallicities, and contributing to understanding Galactic Disk evolution.

Contribution

It provides detailed age, distance, and metallicity estimates for NGC 2425 and NGC 2635, expanding knowledge of intermediate-age open clusters in the Third Galactic Quadrant.

Findings

NGC 2425 is approximately 2.2 Gyr old at 3.5 kpc from the Sun.

NGC 2635 is about 600 Myr old at 4.0 kpc, with extremely low metallicity.

NGC 2635's properties challenge existing Galactic chemical evolution models.

Abstract

We analyse CCD broad band (UBV(RI)c) photometric data obtained in the fields of the poorly studied open clusters NGC 2425 and NGC 2635. Both clusters are found to be of intermediate age thus increasing the population of open clusters known to be of the age of, or older than, the Hyades. More explicitly, we find that NGC 2425 is a 2.2 Gyr old cluster, probably of solar metallicity, located at 3.5 kpc from the Sun. NGC 2635 is a Hyades age (600 Myr) cluster located at a distance of 4.0 kpc from the Sun. Its Colour Magnitude Diagram reveals that it is extremely metal poor for its age and position, thus making it a very interesting object in the context of Galactic Disk chemical evolution models.