En busca de poblaciones múltiples en el cúmulo globular Ruprecht 106 y un método complementario para encontrarlas = Searching for multiple populations in the Globular Cluster Ruprecht 106 and a complementary method to uncover them.

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 at least one GC does not share that behaviour - Ruprecht 106. We analyzed thirteen member red giant branch stars using spectra in the wavelength range 6120-6405 Å obtained through the GIRAFFE Spectrograph, mounted at UT2 telescope at Paranal. We also observed 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. Multiple Populations(MP) in Globular Clusters can be detected both spectroscopically and with appropriate photometric filters. Filters specifically sensitive to light element abundances are particularly effective. One such filter is the classic C(Carbon) filter, one of the original set of Washington System filters. It has proved to be efficient in detecting multiple populations, in combination with the T1 filter in the form of the C − T1 color. In this research we test the ability of a three Washington filter combination, (C − T1) − (T1 − T2). We compare the ability of this color combination with that of the traditional C −T1 color on two globular clusters, NGC 7099 and NGC 1851, types I and II Globular clusters, respectively. Our improved photometry and membership selection, now using Gaia proper motions, finds that the second generation stars are more centrally concentrated than first generation stars, as expected and contrary to our previous findings for NGC 7099. We find that multiple populations are more easily detected in the new (C − T1) − (T1 − T2) color, although C − T1 conserves the best width/error ratio. We also search for differences of both colors while splitting the red-RGB and the blue-RGB in NGC 1851, but no significant improvement was found.