Faint Fuzzy Star Clusters in NGC1023 as Remnants of Merged Star Cluster Complexes

TL;DR

This study uses N-body simulations to demonstrate that faint fuzzy star clusters in NGC1023 are likely remnants of merged young massive cluster complexes, linking observed properties to their formation history.

Contribution

The paper introduces a simulation-based model connecting young cluster complexes in M51 to faint fuzzy clusters in NGC1023, revealing their evolutionary relationship.

Findings

Simulated objects match observed FF sizes and magnitudes.

Objects retain 10-60% of initial mass after 5 Gyr.

Progenitors of FFs are likely merged cluster complexes.

Abstract

In the lenticular galaxy NGC1023 a third population of globular clusters (GCs), called faint fuzzies (FFs), was discovered next to the blue and red GC populations by Larsen & Brodie. While these FFs have colors comparable to the red population, the new population is fainter, larger (R_eff > 7 pc) and, most importantly, shows clear signs of co-rotation with the galactic disk of NGC1023. We present N-body simulations verifying the hypothesis that these disk-associated FFs are related to the young massive cluster complexes (CCs) observed by Bastian et. al in M51, who discovered a mass-radius relation for these CCs. Our models have an initial configuration based on the observations from M51 and are placed on various orbits in a galactic potential derived for NGC1023. All computations end up with a stable object containing 10 to 60% of the initial CC mass after an integration time of 5 Gyr. A conversion to visual magnitudes demonstrates that the resulting objects cover exactly the observed range for FFs. Moreover, the simulated objects show projected half-mass radii between 3.6 and 13.4 pc, in good agreement with the observed FF sizes. We conclude that objects like the young massive CCs in M51 are likely progenitors of the FFs observed in NGC1023.