Globular cluster content and evolutionary history of NGC147

TL;DR

This study spectroscopically confirmed eight globular cluster candidates in NGC147, analyzed their properties, and compared their evolutionary history and system characteristics with other dwarf galaxies.

Contribution

It provides the first complete inventory and detailed properties of NGC147's globular clusters, including metallicities, ages, and abundance ratios, enhancing understanding of dwarf galaxy evolution.

Findings

Confirmed 3 globular clusters in NGC147.

Found lower metallicities in bright clusters compared to galaxy stars.

Estimated mean age of globular clusters as 9+-1 Gyr.

Abstract

We present the results of spectroscopic observations of eight globular cluster candidates in NGC147, a satellite dwarf elliptical galaxy of M31. Our goal is to make a complete inventory of the globular cluster system of this galaxy, determine the properties of their stellar populations, and compare these properties with those of systems of globular clusters in other dwarf galaxies. The candidates were identified on Canada-France-Hawaii telescope photographic plates. Medium resolution spectra were obtained with the SCORPIO spectrograph at the prime focus of the 6m telescope of the Russian Academy of Sciences. We were able to confirm the nature of all eight candidates, three of which (GC5, GC7, and GC10) are indeed globular clusters, and to estimate evolutionary parameters for the two brightest ones and for Hodge II. The bright clusters GC5 and GC7 appear to have metallicities ([Z/H]~ -1.5- -1.8) that are lower than the oldest stars in the galaxy. The fainter GC Hodge II has a metallicity [Z/H]=-1.1 dex, similar to that of the oldest stars in the galaxy. The clusters GC5 and GC7 have low alpha-element abundance ratios. The mean age of the globular clusters in NGC147 is 9+-1 Gyr. The frequency, S_n =6.4, and mass fraction, T=14 of globular clusters in NGC147 appear to be higher than those for NGC185 and 205. (Abridged)