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EnglishBy combining high spatial resolution and wide-field spectroscopy performed, respectively, with SINFONI and FLAMES at the ESO/VLT we measured the radial velocities of more than 600 stars in the direction of NGC 6388, a Galactic globular cluster which is suspected to host an intermediate-mass black hole. Approximately 55% of the observed targets turned out to be cluster members. The cluster velocity dispersion has been derived from the radial velocity of individual stars: 52 measurements in the innermost 2″, and 276 stars located between 18″ and 600″. The velocity dispersion profile shows a central value of ∼13 km s-1, a flat behavior out to ∼60″ and a decreasing trend outward. The comparison with spherical and isotropic models shows that the observed density and velocity dispersion profiles are inconsistent with the presence of a central black hole more massive than ∼2000 M ⊙. These findings are at odds with recent results obtained from integrated light spectra, showing a velocity dispersion profile with a steep central cusp of 23-25 km s-1 at r < 2″ and suggesting the presence of a black hole with a mass of ∼1.7 × 104 M ⊙. We also found some evidence of systemic rotation with amplitude A rot ∼ 8 km s-1 in the innermost 2″ (0.13 pc), decreasing to A rot = 3.2 km s -1 at 18″ < r < 160″.
| Titolo: | The velocity dispersion profile of NGC 6388 from resolved-star spectroscopy: No evidence of a central cusp and new constraints on the black hole mass |
| Autore/i: | LANZONI, BARBARA; MUCCIARELLI, ALESSIO; Origlia L.; Bellazzini M.; FERRARO, FRANCESCO ROSARIO; Valenti E.; MIOCCHI, PAOLO; DALESSANDRO, EMANUELE; PALLANCA, CRISTINA; MASSARI, DAVIDE |
| Autore/i Unibo: | |
| Anno: | 2013 |
| Rivista: | |
| Digital Object Identifier (DOI): | http://dx.doi.org/10.1088/0004-637X/769/2/107 |
| Abstract: | By combining high spatial resolution and wide-field spectroscopy performed, respectively, with SINFONI and FLAMES at the ESO/VLT we measured the radial velocities of more than 600 stars in the direction of NGC 6388, a Galactic globular cluster which is suspected to host an intermediate-mass black hole. Approximately 55% of the observed targets turned out to be cluster members. The cluster velocity dispersion has been derived from the radial velocity of individual stars: 52 measurements in the innermost 2″, and 276 stars located between 18″ and 600″. The velocity dispersion profile shows a central value of ∼13 km s-1, a flat behavior out to ∼60″ and a decreasing trend outward. The comparison with spherical and isotropic models shows that the observed density and velocity dispersion profiles are inconsistent with the presence of a central black hole more massive than ∼2000 M ⊙. These findings are at odds with recent results obtained from integrated light spectra, showing a velocity dispersion profile with a steep central cusp of 23-25 km s-1 at r < 2″ and suggesting the presence of a black hole with a mass of ∼1.7 × 104 M ⊙. We also found some evidence of systemic rotation with amplitude A rot ∼ 8 km s-1 in the innermost 2″ (0.13 pc), decreasing to A rot = 3.2 km s -1 at 18″ < r < 160″. |
| Data prodotto definitivo in UGOV: | 2013-06-27 15:35:10 |
| Data stato definitivo: | 2017-12-01T17:14:19Z |
| Appare nelle tipologie: | 1.01 Articolo in rivista |
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http://hdl.handle.net/11585/153209
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