Radial distribution of the multiple stellar populations in $mathsf{omega}$ Centauri

摘要

Aims. We present a detailed study of the radialdistribution of the multiple populations identified in the Galacticglobular clusterCen.Methods. We used both space-based images (ACS/WFCand WFPC2) and ground-based images (FORS1@VLT and WFI@2.2m ESOtelescopes) to map the cluster from the inner core to the outskirts (20arcmin).These data sets have been used to extract high-accuracy photometry forthe construction of color-magnitude diagrams and astrometric positionsof stars. Results. We find that in the inner 2 core radiithe blue main sequence (bMS) stars slightly dominate the red mainsequence (rMS) in number. Atgreater distances from thecluster center, the relative numbers of bMSstars with respectto rMSdrop steeply, out to 8arcmin, and thenremain constant out to the limit of our observations. We also find thatthe dispersion of the Gaussian that best fits the color distributionwithin the bMS is significantly greater than the dispersion of theGaussian that best fits the color distribution within the rMS. Inaddition, the relative number of intermediate-metallicityred-giant-branch stars (which includes the progeny of the bMS) withrespect to the metal-poor component (theprogeny of the rMS)follows a trend similar to that of the main-sequence star-countratio.The most metal-rich component of the red-giant branch follows the samedistribution as the intermediate-metallicity component. Conclusions. We briefly discuss the possibleimplications of the observed radial distribution of the differentstellar components inCen. Key words: globular clusters: general -globular clusters: individual: Cen [NGC5139] - stars: evolution - stars:populationII - techniques: photometric