Please use this identifier to cite or link to this item:
|Title:||The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters: The Internal Kinematics of the Multiple Stellar Populations in NGC 2808||Authors:||Bellini, A.
Milone, A. P.
van der Marel, R. P.
Marino, A. F.
|Issue Date:||2015||Journal:||THE ASTROPHYSICAL JOURNAL||Number:||810||Issue:||1||First Page:||L13||Abstract:||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 simulation 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. <P />Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.||Acknowledgments:||Support for this work comes from STScI grants for HST programs AR-12845 and GO-13297. E.V. acknowledges support by grant NASA-NNX13AF45G. G.P., S.C., F.D’A. and A.R. acknowledge support from PRIN-INAF 2014 (PI: S. Cassisi).||URI:||http://hdl.handle.net/20.500.12386/23809||URL:||https://iopscience.iop.org/article/10.1088/2041-8205/810/1/L13||ISSN:||0004-637X||DOI:||10.1088/2041-8205/810/1/L13||Bibcode ADS:||2015ApJ...810L..13B||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
Show full item record
Files in This Item:
|Bellini_2015_ApJL_810_L13.pdf||PDF editoriale||413.64 kB||Adobe PDF||View/Open|
checked on Sep 18, 2020
checked on Sep 18, 2020
Items in DSpace are published in Open Access, unless otherwise indicated.