Searching for Multiple Populations in Ruprecht 106

TL;DR

This study confirms that Ruprecht 106 is a unique globular cluster hosting a simple stellar population, unlike most GCs that contain multiple populations, and explores its orbital history suggesting an inner halo origin.

Contribution

The paper provides spectroscopic and photometric evidence confirming Ruprecht 106 as a simple stellar population cluster and investigates its orbital dynamics to assess extragalactic origins.

Findings

Ruprecht 106 hosts a single stellar population.

Spectroscopic and photometric analyses agree on the absence of multiple populations.

Orbital analysis suggests an inner halo origin, not linked to known extragalactic progenitors.

Abstract

More than a decade has passed since the definition of Globular Cluster (GC) changed, and now we know that they host Multiple Populations (MPs). But few GCs do not share that behaviour and Ruprecht 106 is one of these clusters. We analyzed thirteen member red giant branch stars using spectra in the wavelength range 6120-6405 Angstroms obtained through the GIRAFFE Spectrograph, mounted at UT2 telescope at Paranal, as well as the whole cluster using C, V, R and I photometry obtained through the Swope telescope at Las Campanas. Atmospheric parameters were determined from the photometry to determine Fe and Na abundances. A photometric analysis searching for MPs was also carried out. Both analyses confirm that Ruprecht 106 is indeed one on the few GCs to host Simple Stellar Population, in agreement with previous studies. Finally, a dynamical study concerning its orbits was carried out to analyze the possible extra galactic origin of the Cluster. The orbital integration indicates that this GC belongs to the inner halo, while an Energy plane shows that it cannot be accurately associated with any known extragalactic progenitor.