The complex globular cluster system of the S0 galaxy NGC 4382 in the outskirts of the Virgo Cluster

NGC 4382 is a merger-remnant galaxy that has been classified as morphological type E2, S0, and even Sa. In this work, we performed a photometric and spectroscopic analysis of the globular cluster (GC) system of this peculiar galaxy in order to provide additional information about its history. We used a combination of photometric data in different filters, and multiobject and long-slit spectroscopic data obtained using the Gemini/GMOS instrument. The photometric analysis of the GC system, using the Gaussian Mixture Model algorithm in the colour plane, reveals a complex colour distribution within R-gal < 5 arcmin (26.1 kpc), showing four different groups: the typical blue and red subpopulations, a group with intermediate colours, and the fourth group towards even redder colours. From the spectroscopic analysis of 47 GCs, confirmed members of NGC 4382 based on radial velocities, we verified 3 of the 4 photometric groups from the analysis of their stellar populations using the ULySS code. NGC 4382 presents the classic blue (10.4 +/- 2.8 Gyr, [Fe/H] = -1.48 +/- 0.18 dex), and red (12.1 +/- 2.3 Gyr, [Fe/H] = - 0.64 +/- 0.26 dex) GCs formed earlier in the lifetime of the galaxy, and a third group of young GCs (2.2 +/- 0.9 Gyr; [Fe/H] = - 0.05 +/- 0.28 dex). Finally, analysis of long-slit data of the galaxy reveals a luminosity-weighted mean age for the stellar population of similar to 2.7 Gyr, and an increasing metallicity from [Fe/H] = -0.1 to +0.2 dex in R-gal < 10 arcsec (0.87 kpc). These values, and other morphological signatures in the galaxy, are in good agreement with the younger group of GCs, indicating a common origin as a result of a recent merger.

Automated summary

This work analyzes the photometric and spectroscopic properties of the globular cluster system in the peculiar galaxy, NGC 4382. The study reveals a complex color distribution of the globular clusters, confirming the existence of three distinct photometric groups. The spectroscopic analysis indicates the presence of classic blue and red globular clusters, as well as a younger group. The analysis of the galaxy's long-slit data further supports the common origin of the globular clusters and the galaxy, suggesting a recent merger.