The ESO-VLT MIKiS survey reloaded: exploring the internal kinematics of NGC 6440
| Autor: | Leanza, Silvia, Pallanca, Cristina, Ferraro, Francesco R., Lanzoni, Barbara, Dalessandro, Emanuele, Cadelano, Mario, Vesperini, Enrico, Origlia, Livia, Mucciarelli, Alessio, Valenti, Elena |
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| Rok vydání: | 2022 |
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| Druh dokumentu: | Working Paper |
| DOI: | 10.3847/1538-4357/acaaa6 |
| Popis: | In the context of the ESO-VLT Multi-Instrument Kinematic Survey (MIKiS) 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 $\sim 1800$ individual stars distributed over the entire cluster extension, from $\sim$0.1$"$ 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 \sim $ 12 km s$^{-1}$) and no evidence of a central cusp or other significant deviations. Our data allowed 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 $\sim$132 $\pm$ 2{\deg} and an amplitude of $\sim$3 km s$^{-1}$ (corresponding to Vrot/${\sigma}_0 \sim$ 0.3). Also, a flattening of the system qualitatively consistent with the rotation signal has been detected in the central region. Comment: 20 pages, 11 figures, 4 tables, accepted for publication in ApJ |
| Databáze: | arXiv |
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