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Deep Hubble Space Telescope imaging in NGC 6397: Stellar dynamics

Heyl, Jeremy; Richer, Harvey B; Anderson, Jay; Fahlman, Gregory G; Dotter, Aaron; Hurley, Jarrod; Kalirai, Jason S; Rich, R M; Shara, Michael M; Stetson, Peter B; Woodley, Kristin A.; Zurek, D

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Multi-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...[Show more]

dc.contributor.authorHeyl, Jeremy
dc.contributor.authorRicher, Harvey B
dc.contributor.authorAnderson, Jay
dc.contributor.authorFahlman, Gregory G
dc.contributor.authorDotter, Aaron
dc.contributor.authorHurley, Jarrod
dc.contributor.authorKalirai, Jason S
dc.contributor.authorRich, R M
dc.contributor.authorShara, Michael M
dc.contributor.authorStetson, Peter B
dc.contributor.authorWoodley, Kristin A.
dc.contributor.authorZurek, D
dc.date.accessioned2015-12-13T22:41:07Z
dc.identifier.issn0004-637X
dc.identifier.urihttp://hdl.handle.net/1885/78362
dc.description.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.
dc.publisherIOP Publishing
dc.sourceAstrophysical Journal, The
dc.subjectKeywords: astrometry; celestial mechanics; globular clusters: individual (NGC 6397)
dc.titleDeep Hubble Space Telescope imaging in NGC 6397: Stellar dynamics
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume761
dc.date.issued2012
local.identifier.absfor020104 - Galactic Astronomy
local.identifier.ariespublicationf5625xPUB7016
local.type.statusPublished Version
local.contributor.affiliationHeyl, Jeremy, University of British Columbia
local.contributor.affiliationRicher, Harvey B, University of British Columbia
local.contributor.affiliationAnderson, Jay, Space Telescope Science Institute
local.contributor.affiliationFahlman, Gregory G, Herzberg Institute of Astrophysics
local.contributor.affiliationDotter, Aaron, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationHurley, Jarrod, Swinburne University of Technology
local.contributor.affiliationKalirai, Jason S, Space Telescope Science Institute
local.contributor.affiliationRich, R M, University of California
local.contributor.affiliationShara, Michael M, American Museum of Natural History
local.contributor.affiliationStetson, Peter B, National Research Council of Canada
local.contributor.affiliationWoodley, Kristin A., University of British Columbia
local.contributor.affiliationZurek, D, American Museum of Natural History
local.description.embargo2037-12-31
local.bibliographicCitation.issue1
local.bibliographicCitation.startpage51
local.identifier.doi10.1088/0004-637X/761/1/51
dc.date.updated2016-02-24T09:32:36Z
local.identifier.scopusID2-s2.0-84870559751
CollectionsANU Research Publications

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