Young Globular Clusters in an old S0: Clues to the Formation History of NGC 4570

TL;DR

This study uses combined optical and near-infrared photometry of globular clusters in NGC 4570 to uncover a significant population of intermediate-age, metal-rich clusters, shedding light on the galaxy's formation history.

Contribution

It introduces a method combining deep Ks-band photometry with archival HST data to determine ages and metallicities of globular clusters, revealing their formation history.

Findings

Discovery of intermediate-age (1-3 Gyr) globular clusters.

Identification of metal-rich (solar metallicity) clusters.

Evidence of recent star formation episodes in NGC 4570.

Abstract

We here present our first attempt to use Globular Clusters as tracers of their parent galaxy's formation history. Globular Cluster Systems of most early-type galaxies feature two peaks in their optical colour distributions. Blue-peak Globular Clusters are generally believed to be old and metal-poor. The ages, metallicities, and the origin of the red-peak Globular Clusters are being debated. We here present our analysis of the ages and metallicities of the red peak Globular Clusters in the Virgo S0 NGC 4570 using deep Ks-band photometry from NTT/SOFI (ESO program ID 079.B-0511) for the red-peak Globular Clusters in combination with HST-ACS archival data to break the age-metallicity degeneracy. We analyze the combined g, z, and Ks spectral energy distribution by comparison with a large grid of GALEV evolutionary synthesis models for star clusters with different ages and metallicities. This analysis reveals a substantial population of intermediate-age (1-3 Gyr) and metal-rich (solar metallicity) Globular Clusters. We discuss their age and metallicity distributions together with information on the parent galaxy from the literature to gain insight into the formation history of this galaxy. Our results prove the power of this approach to reveal the (violent) star formation and chemical enrichment histories of galaxies on the basis of combined optical and near-infrared photometry.