The ESO-VLT MIKiS survey reloaded: exploring the internal kinematics of NGC 6440

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$0.1$\mathrm{"}$ to 778$\mathrm{"}$ 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$\mathrm{"}$ 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$\mathrm{"}$), revealing a well-defined pattern of ordered rotation with a position angle of the rotation axis of $\sim$132 $\pm$ 2° 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.