Galaxy mass dependence of metal-enrichment of nuclear star clusters

Abstract

Nuclear Star Clusters (NSCs) are commonly found in galaxy centers, but their dominant formation mechanisms remain elusive. We perform a consistent analysis of stellar populations of 97 nearby NSCs, based on VLT spectroscopic data. The sample covers a galaxy stellar mass range of 10${}^7$ to 10${}^{11}$ M${}_{\odot }$ and is more than 3$\times$ larger than any previous studies. We identify three galaxy stellar mass regimes with distinct NSC properties. In the low-mass regime of $\log M_{\mathrm{host}}$ $\lesssim$ 8.5, nearly all NSCs have metallicities lower than circum-NSC host but similar to typical red globular clusters (GCs), supporting the GC inspiral-merger scenario of NSC formation. In the high-mass regime of $\log M_{\mathrm{host}}$ $\gtrsim$ 9.5, nearly all NSCs have higher metallicities than circum-NSC host and red GCs, suggesting significant contributions from in-situ star formation (SF). In the intermediate-mass regime, a comparable fraction of NSCs have higher or lower metallicities than circum-NSC host and red GCs, with no clear dependence on NSC mass, suggesting intermittent in-situ SF. The majority of NSCs with higher metallicities than their host exhibit a negative age$-$metallicity correlation, providing clear evidence of long-term chemical enrichment. The average NSC$-$host metallicity difference peaks broadly around $\log M_{\mathrm{host}}\sim 9.8$ and declines towards both higher and lower galaxy mass. We find that the efficiency of dynamical friction-driven inspiral of GCs observed in present-day galaxies can explain the NSC mass at $\log M_{\mathrm{host}}\lesssim 9.5$ but falls short of observed ones at higher galaxy mass, reinforcing our conclusions based on stellar population analysis.

34 pages, 12 figures, accepted for publication in ApJ

References in corpus (42)

• Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
• Evolutionary Stellar Population Synthesis with MILES. Part I: The Base Models and a New Line Index System
• The ACS Virgo Cluster Survey. VIII. The Nuclei of Early-Type Galaxies
• Updated Nearby Galaxy Catalog
• Nuclear Star Clusters
• The MUSE Hubble Ultra Deep Field Survey: I. Survey description, data reduction and source detection
• The ACS Virgo Cluster Survey. XII. The Luminosity Function of Globular Clusters in Early Type Galaxies
• Galaxy Groups within 3500 km s${}^{-1}$
• Mergers of Stellar-Mass Black Holes in Nuclear Star Clusters
• Clues to Nuclear Star Cluster Formation from Edge-on Spirals
• Galactic Dark Matter Halos and Globular Cluster Populations. III: Extension to Extreme Environments
• The HST/ACS Coma Cluster Survey. X. Nuclear star clusters in low-mass early-type galaxies: scaling relations
• Repeated mergers and ejection of black holes within nuclear star clusters
• The Next Generation Virgo Cluster Survey. VI. The Kinematics of Ultra-compact Dwarfs and Globular Clusters in M87
• The Globular Cluster Migratory Origin of Nuclear Star Clusters
• New insights on the formation of nuclear star clusters
• ELVES II: GCs and Nuclear Star Clusters of Dwarf Galaxies; The Importance of Environment
• Diversity of nuclear star cluster formation mechanisms revealed by their star formation histories
• Virgo Redux: The Masses and Stellar Content of Nuclei in Early-Type Galaxies from Multi-Band Photometry and Spectroscopy
• Luminosity Models and Density Profiles for Nuclear Star Clusters for a Nearby Volume-Limited Sample of 29 Galaxies
• Metal-poor nuclear star clusters in two dwarf galaxies near Centaurus A suggesting formation from the in-spiraling of globular clusters
• The nucleation fraction of Local Volume galaxies
• The Dark Matter Distributions in Low-Mass Disk Galaxies. II. The Inner Density Profiles
• The Next Generation Virgo Cluster Survey. XXXIV. Ultra-Compact Dwarf (UCD) Galaxies in the Virgo Cluster
• A deep view into the nucleus of the Sagittarius Dwarf Spheroidal Galaxy with MUSE. II. Kinematic characterization of the stellar populations
• An evolutionary continuum from nucleated dwarf galaxies to star clusters
• Nuclear star cluster formation in star-forming dwarf galaxies
• Disentangling the formation mechanisms of nuclear star clusters
• The Next Generation Fornax Survey (NGFS): VII. A MUSE view of the nuclear star clusters in Fornax dwarf galaxies
• Investigating the Stellar Mass Growth Histories of Satellite Galaxies as a Function of Infall Time using Phase-Space
• Growing Black Holes through Successive Mergers in Galactic Nuclei: I. Methods and First Results
• sMILES SSPs: A Library of Semi-Empirical MILES Stellar Population Models with Variable [$\alpha$/Fe] Abundances
• The MBHBM${}^{\star }$ Project -- II. Molecular Gas Kinematics in the Lenticular Galaxy NGC 3593 Reveal a Supermassive Black Hole
• Photometric and Structural Parameters of Newly Discovered Nuclear Star Clusters in Local Volume Galaxies
• PHANGS-JWST First Results: A combined HST and JWST analysis of the nuclear star cluster in NGC 628
• Starbursting Nuclei in Old Dwarf Galaxies
• Contribution of stripped nuclei to the ultracompact dwarf galaxy population in the Virgo Cluster
• On the link between nuclear star cluster and globular cluster system mass, nucleation fraction and environment
• Discovery of a Bimodal Environmental Distribution of Compact Ellipticals in the Local Universe
• Are we observing a NSC in course of formation in the NGC 4654 galaxy?
• Evidence for globular cluster collapse after a dwarf-dwarf merger: A potential nuclear star cluster in formation
• Unveiling the formation of NGC 2915 with MUSE: A counter-rotating stellar disk embedded in a disordered gaseous environment

Cited by in corpus (1)

• The Nuclear Star Cluster of M 74: a fossil record of the very early stages of a star-forming galaxy