A census of new globular clusters in the Galactic bulge

TL;DR

This paper provides a comprehensive census of 41 newly discovered globular clusters in the Galactic bulge, analyzing their properties and comparing them to known clusters to understand their origins and characteristics.

Contribution

It compiles and analyzes recent discoveries of globular clusters, revealing their faintness, metallicity distribution, and age-metallicity relations, enhancing understanding of bulge cluster populations.

Findings

New clusters are faint with M_V around -6.0 mag.

Metallicity peaks at [Fe/H] ~ -1.08 and -0.51 dex.

Old clusters show no age-metallicity relation, indicating in situ formation.

Abstract

The number of known globular clusters in the Galactic bulge has been increasing steadily thanks to different new surveys. The aim of this study is to provide a census of the newly revealed globular clusters in the Galactic bulge, and analyze their characteristics. In recent years, many globular clusters have been discovered or identified. The stellar populations to which they belong are indicated in their original studies: they are mostly bulge clusters, with some identified as disk or halo members. We collected 41 new globular clusters revealed in the last decade and compared them to the known bulge clusters. The new clusters are intrinsically faint with $M_V$ of around -6.0 mag. The distance to the Sun of the ensemble of well-known and new bulge clusters is compatible with the Galactocentric distance measurements from the Galactic black hole location. The ensemble sample shows metallicity peaks at [Fe/H] ~ -1.08 $\pm$ 0.35 and -0.51 $\pm$ 0.25 dex, confirming previous findings. The age-metallicity relation of the new clusters younger than 10 Gyr is compatible with that of the ex situ samples of the dwarf galaxies Sagittarius, Canis Majoris, and Gaia-Enceladus-Sausage. The clusters with ages between 11.5 and 13.5 Gyr show no age-metallicity relation, because they are all old. This is compatible with their formation in situ in the early Galaxy.