In the context of the ESO-VLT Multi-Instrument Kinematic Survey of Galactic globular clusters, here we present the line-of-sight velocity dispersion profile of NGC 6440, a massive globular cluster located in the Galactic bulge. By combining the data acquired with four different spectrographs, we obtained the radial velocity of a sample of similar to 1800 individual stars distributed over the entire cluster extension, from similar to 0.'' 1 to 778 '' from the center. Using a properly selected sample of member stars with the most reliable radial velocity measures, we derived the velocity dispersion profile up to 250 '' from the center. The profile is well described by the same King model that best fits the projected star density distribution, with a constant inner plateau (at sigma (0) similar to 12 km s(-1)) and no evidence of a central cusp or other significant deviations. Our data allowed us to study the presence of rotation only in the innermost regions of the cluster (r < 5 ''), revealing a well-defined pattern of ordered rotation with a position angle of the rotation axis of similar to 132 degrees +/- 2 degrees and an amplitude of similar to 3 km s(-1) (corresponding to V (rot)/sigma (0) similar to 0.3). In addition, a flattening of the system qualitatively consistent with the rotation signal has been detected in the central region.
Silvia Leanza, Cristina Pallanca, Francesco R. Ferraro, Barbara Lanzoni, Emanuele Dalessandro, Mario Cadelano, et al. (2023). The ESO-VLT MIKiS Survey Reloaded: Exploring the Internal Kinematics of NGC 6440*. THE ASTROPHYSICAL JOURNAL, 944(2), 1-14 [10.3847/1538-4357/acaaa6].
The ESO-VLT MIKiS Survey Reloaded: Exploring the Internal Kinematics of NGC 6440*
Silvia Leanza
;Cristina Pallanca;Francesco R. FerraroSupervision
;Barbara Lanzoni;Mario Cadelano;Alessio Mucciarelli;
2023
Abstract
In the context of the ESO-VLT Multi-Instrument Kinematic Survey of Galactic globular clusters, here we present the line-of-sight velocity dispersion profile of NGC 6440, a massive globular cluster located in the Galactic bulge. By combining the data acquired with four different spectrographs, we obtained the radial velocity of a sample of similar to 1800 individual stars distributed over the entire cluster extension, from similar to 0.'' 1 to 778 '' from the center. Using a properly selected sample of member stars with the most reliable radial velocity measures, we derived the velocity dispersion profile up to 250 '' from the center. The profile is well described by the same King model that best fits the projected star density distribution, with a constant inner plateau (at sigma (0) similar to 12 km s(-1)) and no evidence of a central cusp or other significant deviations. Our data allowed us to study the presence of rotation only in the innermost regions of the cluster (r < 5 ''), revealing a well-defined pattern of ordered rotation with a position angle of the rotation axis of similar to 132 degrees +/- 2 degrees and an amplitude of similar to 3 km s(-1) (corresponding to V (rot)/sigma (0) similar to 0.3). In addition, a flattening of the system qualitatively consistent with the rotation signal has been detected in the central region.File | Dimensione | Formato | |
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