Homogeneous metallicities and radial velocities for Galactic globular clusters. II. New CaT metallicities for 28 distant and reddened globular clusters

TL;DR

This study provides new homogeneous metallicity and radial velocity measurements for 28 distant and reddened Galactic globular clusters using CaII triplet spectroscopy, enhancing the understanding of their properties and distributions.

Contribution

It adds metallicity and radial velocity data for 28 globular clusters, many studied spectroscopically for the first time, increasing the overall homogeneous dataset for Galactic globular clusters.

Findings

Approximately 69% of clusters now have homogeneous measurements.

First spectroscopic analysis for most clusters based on individual stars.

Potential intrinsic metallicity spread identified in NGC 6256.

Abstract

Although the globular clusters in the Milky Way have been studied for a long time, a significant fraction of them lack homogeneous metallicity and radial velocity measurements. In an earlier paper we presented the first part of a project to obtain metallicities and radial velocities of Galactic globular clusters from multiobject spectroscopy of their member stars using the ESO Very Large Telescope. In this paper we add metallicities and radial velocities for a new sample of 28 globular clusters, including in particular globular clusters in the MW halo and the Galactic bulge. Together with our previous results, this study brings the number of globular clusters with homogeneous measurements to $\sim 69$ \% of those listed in the W. Harris' catalogue. As in our previous work, we have used the CaII triplet lines to derive metallicities and radial velocities. For most of the clusters in this study, this is the first analysis based on spectroscopy of individual member stars. The metallicities derived from the CaII triplet are then compared to the results of our parallel study based on spectral fitting in the optical region and the implications for different calibrations of the CaII triplet line strengths are discussed. We also comment on some interesting clusters and investigate the presence of an abundance spread in the globular clusters here. A hint of a possible intrinsic spread is found for NGC 6256, which therefore appears to be a good candidate for further study.