SCYON Abstract

Received on September 05 2011

Outer density profiles of Galactic globular clusters

AuthorsJ. Carballo-Bello (1,2), M. Gieles (3), A. Sollima (4), S. Koposov (3,6), D. Martinez-Delgado (5) and Jorge Penarrubia (3)
Affiliation(1) Instituto de Astrofisica de Canarias (IAC), Via Lactea s/n, La Laguna E-38205, S/C de Tenerife, Spain
(2) Departamento de Astrofisica, Universidad de La Laguna, La Laguna E-38205, S/C de Tenerife, Spain
(3) Institute of Astronomy, University of Cambridge, CB3 0HA Cambridge, United Kingdom
(4) INAF- Observatorio Astronomico di Padova, I35122 Padova, Italy
(5) Max Planck Institut für Astronomie, D69117 Heidelberg, Germany
(6) Sternberg Astronomical Institute, Universitetskiy pr. 13, 119992 Moscow, Russia
Accepted byMonthly Notices of the Royal Astronomical Society
Contactjacb@iac.es
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Abstract

Using deep photometric data from WFC@INT and WFI@ESO2.2m we measure the outer number density profiles of 19 stellar clusters located in the inner region of the Milky Way halo (within a Galactocentric distance range of 10--30 kpc) in order to assess the impact of internal and external dynamical processes on the spatial distribution of stars. Adopting power-law fitting templates, with index -γ in the outer region, we find that the clusters in our sample can be divided in two groups: a group of massive clusters (≥ 105 M(sun)) that has relatively flat profiles with 2.5 < γ < 4 and a group of low-mass clusters (≤ 105 M(sun)), with steep profiles (γ > 4) and clear signatures of interaction with the Galactic tidal field. We refer to these two groups as 'tidally unaffected' and 'tidally affected', respectively. Our results also show a clear trend between the slope of the outer parts and the half-mass density of these systems, which suggests that the outer density profiles may retain key information on the dominant processes driving the dynamical evolution of Globular Clusters.