Globular clusters (GCs) are excellent tracers of the formation and early evolution of the Milky Way. The bulge GCs (BGCs) are particularly important because they can reveal vital information about the oldest, in-situ component of the Milky Way. We aim at deriving mean metallicities and radial velocities for 13 GCs that lie towards the bulge and are generally associated with this component. This region is observationally challenging because of high extinction and stellar density, hampering optical studies of these and similar BGCs, making most previous determinations of these parameters quite uncertain. We use near infrared low resolution spectroscopy with the FORS2 instrument on the VLT to measure the wavelengths and equivalent widths of the CaII triplet (CaT) lines for a number of stars per cluster. We derive radial velocities, ascertain membership and apply known calibrations to determine metallicities for cluster members, for a mean of 11 members per cluster. Unfortunately, one of our targets, VVV-GC002, which is the closest GC to the Galactic center, turned out not to have any members in our sample. We derive mean cluster RV values to 3km/s, and mean metallicities to 0.05dex. We find generally good agreement with previous determinations for both metallicity and velocity. On average, our metallicities are 0.07dex more metal-rich than Harris (2010, https://physics.mcmaster.ca/%7Eharris/mwgc.dat), with a standard deviation of the difference of 0.25dex. Our sample has metallicities lying between -0.21 and -1.64 and is distributed between the traditional metal-rich BGC peak near [Fe/H]~-0.5 and a more metal-poor peak around [Fe/H]~-1.1, which has recently been identified. These latter are candidates for the oldest GCs in the Galaxy, if blue horizontal branches are present, and include BH261, NGC6401, NGC6540, NGC6642, and Terzan 9. Finally, Terzan 10 is even more metal-poor. However, dynamically, Terzan 10 is likely an intruder from the halo, possibly associated with the Gaia-Enceladus or Kraken accretion events. Terzan 10 is also confirmed as an Oosterho type II GC based on our results. The CaT technique is an excellent method for deriving mean metallicities and velocities for heavily obscured GCs. Our sample provides reliable mean values for both of these key properties for an important sample of previously poorly-studied BGCs from spectroscopy of a significant number of members per cluster. We emphasize that the more metal-poor GCs are excellent candidates for being ancient relics of bulge formation. The lone halo intruder in our sample, Terzan 10, is conspicuous for also having by far the lowest metallicity, and casts doubt on the possibility of any bonafide BGCs at metallicities below about ~-1.5.

Cone search capability for table J/A+A/669/A115/table1 (Observed Bulge globular clusters)

Cone search capability for table J/A+A/669/A115/table2 (Measured values for member stars)