Properties of the Young Milky Way Globular Cluster Whiting 1 from Near-Infrared Photometry

TL;DR

This study uses near-infrared photometry and isochrone fitting to determine that Whiting 1 is a young, moderately metal-rich globular cluster, providing new insights into its properties and environment.

Contribution

It applies near-infrared isochrone fitting to refine the fundamental parameters of Whiting 1, confirming its youth and metallicity, and identifies a background galaxy cluster affecting its photometry.

Findings

Whiting 1 is approximately 5.7 Gyr old.

The cluster has a metallicity of [Fe/H] ≈ -0.5.

A background galaxy cluster at z≈1 was detected near Whiting 1.

Abstract

Whiting 1 is a member of the fast-growing group of young globular clusters in the Milky Way halo. Preliminary estimates of its fundamental parameters have been provided using optical photometry and low resolution spectroscopy. In an attempt to strengthen our knowledge of Whiting 1, in this study we employ a complementary approach. Isochrone fitting method was applied on the Near-Infrared Color-Magnitude Diagram and yields an age t=5.7$\pm$0.3 Gyr, metallicity $z$=0.006$\pm$0.001 ([Fe/H]=$-$0.5$\pm$0.1) and distance modulus $(m-M)_0$=17.48$\pm$0.10. Our results confirm that Whiting 1 is a young and moderately metal-rich globular cluster. It is one of the youngest from the Sgr dSph. We fitted an Elson, Fall and Freeman (EFF) profile to the near-infrared number counts, and measured cluster core radius $r_c$=9.1${\prime\prime}$$\pm$3.9${\prime\prime}$. Two probable eclipsing variables in the cluster were found from multi-epoch $V$ band photometry. Finally, an unknown galaxy cluster was identified on our $K$ vs. $(J-K)$ color-magnitude diagram. It has a redshift z$\sim$1, and it is located at about 1${\prime}$ from the center of Whiting 1 at $\alpha_{J2000}=02^{h} 02^{m} 56.6^{s}$, $\delta_{J2000}=-03^{\circ} 16{\prime} 09{\prime\prime}$, contaminating the cluster photometry.