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Title: THE HUBBLE SPACE TELESCOPE UV LEGACY SURVEY OF GALACTIC GLOBULAR CLUSTERS: THE INTERNAL KINEMATICS OF THE MULTIPLE STELLAR POPULATIONS IN NGC 2808

Numerous observational studies have revealed the ubiquitous presence of multiple stellar populations in globular clusters and cast many difficult challenges for the study of the formation and dynamical history of these stellar systems. In this Letter we present the results of a study of the kinematic properties of multiple populations in NGC 2808 based on high-precision Hubble Space Telescope proper-motion measurements. In a recent study, Milone et al. identified five distinct populations (A–E) in NGC 2808. Populations D and E coincide with the helium-enhanced populations in the middle and the blue main sequences (mMS and bMS) previously discovered by Piotto et al.; populations A–C correspond to the redder main sequence that, in Piotto et al., was associated with the primordial stellar population. Our analysis shows that, in the outermost regions probed (between about 1.5 and 2 times the cluster half-light radius), the velocity distribution of populations D and E is radially anisotropic (the deviation from an isotropic distribution is significant at the ∼3.5σ level). Stars of populations D and E have a smaller tangential velocity dispersion than those of populations A–C, while no significant differences are found in the radial velocity dispersion. We present the results of a numerical simulationmore » showing that the observed differences between the kinematics of these stellar populations are consistent with the expected kinematic fingerprint of the diffusion toward the cluster outer regions of stellar populations initially more centrally concentrated.« less
Authors:
; ;  [1] ; ;  [2] ;  [3] ; ;  [4] ; ;  [5] ;  [6] ;  [7]
  1. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
  2. Department of Astronomy, Indiana University, Bloomington, IN 47405 (United States)
  3. Dipartimento di Fisica e Astronomia “Galileo Galilei,” Università di Padova, v.co dell’Osservatorio 3, I-35122, Padova (Italy)
  4. Research School of Astronomy and Astrophysics, Australian National University, Mt Stromlo Observatory, via Cotter Rd, Weston, ACT 2611 (Australia)
  5. Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Padova, v.co dell’Osservatorio 5, I-35122, Padova (Italy)
  6. Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Teramo, Via Mentore Maggini s.n.c., I-64100, Teramo (Italy)
  7. Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Roma, Via Frascati 33, I-00040, Monteporzio Catone, Roma (Italy)
Publication Date:
OSTI Identifier:
22518895
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 810; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANISOTROPY; COMPUTERIZED SIMULATION; DIFFUSION; GALAXIES; HELIUM; METHYL METHANESULFONATE; PROPER MOTION; RADIAL VELOCITY; SPACE; STAR CLUSTERS; STARS; TELESCOPES; VISIBLE RADIATION