Kinematics of a globular cluster with an extended profile: NGC 5694

Michele Bellazzini, Alessio Mucciarelli, Antonio Sollima, M Catelan, Emanuele Dalessandro, M Correnti, V. D'Orazi, C. Cortés, P Amigo

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We present a study of the kinematics of the remote globular cluster NGC 5694 based on GIRAFFE@VLT medium-resolution spectra. A sample of 165 individual stars selected to lie on the red giant branch in the cluster colour-magnitude diagram was considered. Using radial velocity and metallicity from Calcium triplet, we were able to select 83 bona fide cluster members. The addition of six previously known members leads to a total sample of 89 cluster giants with typical uncertainties ≤1.0 kms-1 in their radial velocity estimates. The sample covers a wide range of projected distances from the cluster centre, from~0.2 arcmin to 6.5 arcmin (minus tilde)(combining long vertical line 23 half-light radii (rh).We find only very weak rotation, as typical of metal-poor globular clusters. The velocity dispersion gently declines from a central value of s σ=6.1 kms-1 to s (minus tilde)(combining long vertical line 2.5 kms-1 at ~2 arcmin (minus tilde)(combining long vertical line 7.1rh, then it remains flat out to the next (and last) measured point of the dispersion profile, at ~4 arcmin (minus tilde)(combining long vertical line 14.0rh, at odds with the predictions of isotropic King models. We show that both isotropic single-mass non-collisional models and multimass anisotropic models can reproduce the observed surface brightness and velocity dispersion profiles.

Original languageEnglish
Pages (from-to)3130-3138
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
Publication statusPublished - 2015


  • Globular clusters: Individual: NGC 5694
  • Stars: Abundances

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