Spectroscopic study of globular and fuzzy clusters in Lenticular galaxy NGC 1023

TL;DR

This study uses spectroscopy to analyze globular and fuzzy clusters in NGC 1023, revealing their ages, metallicities, and kinematics, and providing new insights into their origins and evolution within the galaxy.

Contribution

First spectroscopic measurements of ages and metallicities of fuzzy clusters in a galaxy, confirming their younger age and disk association compared to globular clusters.

Findings

Fuzzy clusters are younger (7-9 Gyr) than globular clusters (>10 Gyr).

Both cluster types are metal-rich with [Fe/H] ≈ -0.58.

Fuzzy clusters are associated with the galaxy's disk.

Abstract

We here report the results from spectroscopic observations of a sample of 26 globular cluster (GC) and 21 faint fuzzy (FF) candidates in the lenticular galaxy NGC 1023 using the 10.4-m Gran Telescopio Canarias. Using the recessional velocities and stellar absorption features, we determine that 18 and 9 of the observed candidates are bona fide GCs and FFs, respectively. The majority of the rejected FF candidates are background emission line galaxies for which we determine their redshifts. We used the spectroscopic data to determine velocity, age, metallicity and extinction of all bona fide clusters. We find that FFs are clearly younger (age = 7-9 Gyr) than GCs (age > 10 Gyr). Both kind of clusters in this galaxy are metal-rich ([Fe/H] = -0.58 $\pm$ 0.33). The ages and metallicities of individual FFs reported here are the first such measurements in any galaxy and agree with the previously-reported measurement on stacked spectrum. The kinematical analysis reaffirms that the FFs belong to the disk of the galaxy, suggesting that their progenitors are most likely massive, compact disk clusters that have been able to survive for long timescales. We propose that the fuzzy appearance of FFs as compared to the GCs is a consequence of the dynamical evolution of their progenitor super star clusters in the disks of low-mass galaxies.