Deep Hubble Space Telescope imaging in NGC 6397: stellar dynamics

Download
  1. Get@NRC: Deep Hubble Space Telescope imaging in NGC 6397: stellar dynamics (Opens in a new window)
DOIResolve DOI: http://doi.org/10.1088/0004-637X/761/1/51
AuthorSearch for: ; Search for: ; Search for: ; Search for: ; Search for: ; Search for: ; Search for: ; Search for: ; Search for: ; Search for: ; Search for: ; Search for:
TypeArticle
Journal titleThe Astrophysical Journal
ISSN0004-637X
Volume761
Issue1
Article number51
AbstractMulti-epoch observations with the Advanced Camera for Surveys on the Hubble Space Telescope provide a unique and comprehensive probe of stellar dynamics within NGC 6397. We are able to confront analytic models of the globular cluster with the observed stellar proper motions. The measured proper motions probe well along the main sequence from 0.8 to below 0.1 M as well as white dwarfs younger than 1 Gyr. The observed field lies just beyond the half-light radius where standard models of globular cluster dynamics (e.g., based on a lowered Maxwellian phase-space distribution) make very robust predictions for the stellar proper motions as a function of mass. The observed proper motions show no evidence for anisotropy in the velocity distribution; furthermore, the observations agree in detail with a straightforward model of the stellar distribution function. We do not find any evidence that the young white dwarfs have received a natal kick in contradiction with earlier results. Using the observed proper motions of the main-sequence stars, we obtain a kinematic estimate of the distance to NGC 6397 of 2.2+0.5 - 0.7 kpc and a mass of the cluster of 1.1 ± 0.1 × 105 M at the photometric distance of 2.53 kpc. One of the main-sequence stars appears to travel on a trajectory that will escape the cluster, yielding an estimate of the evaporation timescale, over which the number of stars in the cluster decreases by a factor of e, of about 3 Gyr. The proper motions of the youngest white dwarfs appear to resemble those of the most massive main-sequence stars, providing the first direct constraint on the relaxation time of the stars in a globular cluster of greater than or about 0.7 Gyr. © 2012. The American Astronomical Society. All rights reserved..
Publication date
LanguageEnglish
AffiliationNational Science Infrastructure; National Research Council Canada
Peer reviewedYes
NPARC number21270047
Export citationExport as RIS
Report a correctionReport a correction
Record identifierdac4a2b6-5f80-4a8a-a7d8-3b4de14ca3a7
Record created2013-12-16
Record modified2016-05-09
Bookmark and share
  • Share this page with Facebook (Opens in a new window)
  • Share this page with Twitter (Opens in a new window)
  • Share this page with Google+ (Opens in a new window)
  • Share this page with Delicious (Opens in a new window)