Properties of the Young Milky Way globular cluster Whiting 1 from near-infrared photometry

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 colour-magnitude diagram and yields an age t = 5.7 ± 0.3 Gyr, metallicity z = 0.006 ± 0.001 ([Fe/H] = -0.5 ± 0.1) and distance modulus (m - M)₀ = 17.48 ± 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 arcsec ± 3.9 arcsec. 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 versus (J - K) colour-magnitude diagram. It has a redshift z ∼ 1, and it is located at about 1 arcmin from the centre of Whiting 1 at α _J2000 = 02^h 02^m 56 {.^{{s}}}6, δ_J2000 = -03°16^'09^'', contaminating the cluster photometry.