We report the detection of a stellar density cusp and a velocity dispersion increase in the center of the globular cluster M54, located at the center of the Sagittarius dwarf galaxy (Sgr). The central line-of-sight velocity dispersion is 20.2 ± 0.7 km s-1, decreasing to 16.4 ± 0.4 km s-1 at 2farcs5 (0.3 pc). Modeling the kinematics and surface density profiles as the sum of a King model and a point-mass yields a black hole mass of ~9400 M sun. However, the observations can alternatively be explained if the cusp stars possess moderate radial anisotropy. A Jeans analysis of the Sgr nucleus reveals a strong tangential anisotropy, probably a relic from the formation of the system.

Density and Kinematic Cusps in M54 at the Heart of the Sagittarius Dwarf Galaxy: Evidence for A 104 M sun Black Hole? / Ibata, R.; Bellazzini, M.; Chapman, S. C.; Dalessandro, Emanuele; Ferraro, FRANCESCO ROSARIO; Irwin, M.; Lanzoni, Barbara; Lewis, G. F.; Mackey, A. D.; Miocchi, Paolo; Varghese, A.. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - STAMPA. - 699(2010), pp. L169-L173.

Density and Kinematic Cusps in M54 at the Heart of the Sagittarius Dwarf Galaxy: Evidence for A 104 M sun Black Hole?

DALESSANDRO, EMANUELE;FERRARO, FRANCESCO ROSARIO;LANZONI, BARBARA;MIOCCHI, PAOLO;
2010

Abstract

We report the detection of a stellar density cusp and a velocity dispersion increase in the center of the globular cluster M54, located at the center of the Sagittarius dwarf galaxy (Sgr). The central line-of-sight velocity dispersion is 20.2 ± 0.7 km s-1, decreasing to 16.4 ± 0.4 km s-1 at 2farcs5 (0.3 pc). Modeling the kinematics and surface density profiles as the sum of a King model and a point-mass yields a black hole mass of ~9400 M sun. However, the observations can alternatively be explained if the cusp stars possess moderate radial anisotropy. A Jeans analysis of the Sgr nucleus reveals a strong tangential anisotropy, probably a relic from the formation of the system.
Ibata, R.; Bellazzini, M.; Chapman, S. C.; Dalessandro, Emanuele; Ferraro, FRANCESCO ROSARIO; Irwin, M.; Lanzoni, Barbara; Lewis, G. F.; Mackey, A. D.; Miocchi, Paolo; Varghese, A.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11585/79114
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