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

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±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 ′′ ±3.9 ′′ . 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∼1, and it is located at about 1 ′ from the center of Whiting 1 at α J2000 = 02 h 02 m 56.6 s , δ J2000 = −03• 16 ′ 09 ′′ , contaminating the cluster photometry.

The southern leading and trailing wraps of the Sagittarius tidal stream around the globular cluster Whiting 1

“…Whiting 1 is a 6 Gyr old Galactic GC that has been associated with Sgr because of its projected position, distance (d ∼ 30 kpc) and radial velocity (v r ∼ −130 km s −1 ), which are consistent with theoretical predictions for the stream in that region (Carraro et al 2007;Law & Majewski 2010b;Koposov et al 2012;Valcheva et al 2015). Forbes & Bridges (2010) have shown that this cluster fits in the age-metallicity relation followed by other globulars associated with Sgr.…”

Evidence That Hydra I Is a Tidally Disrupting Milky Way Dwarf Galaxy

“…If Hydra I is a disrupting GC, then we expect it to contain (to first order) a single stellar population with the age of ∼ 5−6 Gyr as inferred from our stellar populations Hansen et al (2013), Valcheva et al (2015), and Rosenberg et al (1998a,b), respectively, are also included and labeled. As in Dotter et al (2011), individual analysis (Section 4.3).…”

“…The MW has few known, well studied GCs in the intermediate age (∼ 6−8 Gyr) range. These include Pal 1 (Rosenberg et al 1998a,b), Pal 12, Terzan 7 (Dotter et al 2010), Whiting 1 (Valcheva et al 2015), and 47 Tuc (Hansen et al 2013). With the exception of Whiting 1, all of these GCs have galactocentric distances 18 kpc (Harris 1996), similar to that of Hydra I (d MW = 19 kpc).…”

A nitrogen-enhanced metal-poor star discovered in the globular cluster ESO280−SC06

“…Spectroscopic, astrometric, and photometric observations have been undertaken with the aim of confirming, constraining, and ruling out the various proposed formation mechanisms of these multiple stellar populations (for an overview of the various proposals see the reviews of Charbonnel 2016; Bastian & Lardo 2018;Forbes et al 2018, and references therein). As the 'typical' clusters have not shown a clear path forward, there is now much interest in exploring the edges of the parameter space: the least massive clusters (e.g., Mucciarelli et al 2016;Simpson et al 2017b), the 'youngest' clusters (e.g., Valcheva et al 2014;Hollyhead et al 2016), and young massive clusters in other galaxies that are thought to be to precursors to the ancient globular clusters of the Milky Way (e.g., Cabrera-Ziri et al 2016, but see discussion in Renaud 2018Renaud , 2019 on whether these objects are truly analogues to present-day globular clusters). It is in this context that we have been investigating the very metal-poor globular cluster ESO280-SC06.…”