Disentangling the formation mechanisms of nuclear star clusters

Abstract

Nuclear star clusters (NSCs) are massive star clusters found ubiquitously in the centres of galaxies, from the dwarf regime to massive ellipticals and spirals. The fraction of nucleated galaxies is as high as $>$ 90 % at $M_{\text{gal}}\sim 10^9{M}_{\odot }$. However, how NSC formation mechanisms work in different regimes and what determines galaxy nucleation is still unclear. The dissipationless accretion of infalling globular clusters (GCs) and the in situ formation of stars directly at the galactic centre likely operate to grow NSCs in most galaxies; however, their efficiency has been difficult to assess observationally. Here, we provide, for the first time, a quantitative determination of the relative strength of these processes in the build-up of individual NSCs. Using a semi-analytical model of NSC formation based on the orbital evolution of inspiraling GCs, together with observed NSC and GC system properties, we derived the mass fraction of in situ born stars $f_{\text{in, NSC}}$ for 119 galaxies with masses from $3\times 10^7$ to $3\times 10^{11}{M}_{\odot }$, in the Local Volume, the Fornax, and Virgo galaxy clusters. Our analysis reveals that the NSC mass, as well as the ratio of NSC to the total GC system mass, are strong indicators of the dominant NSC formation channel, and not the total galaxy stellar mass as previously suggested. More massive NSCs formed predominantly via the in situ formation of stars ($f_{\text{in, NSC}}\sim 0.9$), while the lower-mass NSCs are expected to have formed predominantly through the merger of GCs ($f_{\text{in, NSC}}\sim 0.2$). The results of this simple model are in agreement with recent independent estimates of the dominant NSC formation channel from recent stellar population analysis.

11 pages, 7 figures, accepted for publication in A&A

References in corpus (25)

• The ACS Virgo Cluster Survey. VIII. The Nuclei of Early-Type Galaxies
• UV-extended E-MILES stellar population models: young components in massive early-type galaxies
• The ACS Virgo Cluster Survey XV. The Formation Efficiencies of Globular Clusters in Early-Type Galaxies: The Effects of Mass and Environment
• The ACS Fornax Cluster Survey. I. Introduction to the Survey and Data Reduction Procedures
• Large scale kinematics and dynamical modelling of the Milky Way nuclear star cluster
• The HST/ACS Coma Cluster Survey. X. Nuclear star clusters in low-mass early-type galaxies: scaling relations
• Globular Cluster Systems in Nearby Dwarf Galaxies: I. HST/ACS Observations and Dynamical Properties of Globular Clusters at Low Environmental Density
• KMOS view of the Galactic Centre - II. Metallicity distribution of late-type stars
• Improved Dynamical Constraints on the Mass of the central Black Hole in NGC 404
• Merging of globular clusters within inner galactic regions. II. The Nuclear Star Cluster formation
• The Structure of Nuclear Star Clusters in Nearby Late-type Spiral Galaxies from Hubble Space Telescope Wide Field Camera 3 Imaging
• New insights on the formation of nuclear star clusters
• On the rotation of nuclear star clusters formed by cluster-inspirals
• An EAGLE's View of Ex-situ Galaxy Growth
• A deep view into the nucleus of the Sagittarius Dwarf Spheroidal Galaxy with MUSE. I. Data and stellar population characterization
• 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
• Dissipative transformation of non-nucleated dwarf galaxies into nucleated systems
• Metal-poor nuclear star clusters in two dwarf galaxies near Centaurus A suggesting formation from the in-spiraling of globular clusters
• Detailed Abundances for the Old Population near the Galactic Center: I. Metallicity distribution of the Nuclear Star Cluster
• The ACS Fornax Cluster Survey. III. Globular Cluster Specific Frequencies of Early-Type Galaxies
• Bar-Driven Mass Build-Up within the Central 50pc of NGC6946
• On the origin of a rotating metal-poor stellar population in the Milky Way Nuclear Cluster
• Revealing the Formation of the Milky Way Nuclear Star Cluster via Chemo-Dynamical Modeling
• The Next Generation Fornax Survey (NGFS): VII. A MUSE view of the nuclear star clusters in Fornax dwarf galaxies

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• Growing Black Holes through Successive Mergers in Galactic Nuclei: I. Methods and First Results
• Euclid: Early Release Observations -- Globular clusters in the Fornax galaxy cluster, from dwarf galaxies to the intracluster field
• Photometric and Structural Parameters of Newly Discovered Nuclear Star Clusters in Local Volume Galaxies
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• Gravitational waves from mergers of Population III binary black holes: roles played by two evolution channels
• Effect of the initial mass function on the dynamical SMBH mass estimate in the nucleated early-type galaxy FCC 47
• PHANGS-JWST First Results: A combined HST and JWST analysis of the nuclear star cluster in NGC 628
• A Deep View into the Nucleus of the Sagittarius Dwarf Spheroidal Galaxy with MUSE. III. Discrete multi-component population-dynamical models based on the Jeans equations
• On the link between nuclear star cluster and globular cluster system mass, nucleation fraction and environment
• The puzzle of isolated and quenched dwarf galaxies in cosmic voids
• LISA Constraints on an Intermediate-Mass Black Hole in the Galactic Centre
• An Enhanced Massive Black Hole Occupation Fraction Predicted in Cluster Dwarf Galaxies
• Evidence of star cluster migration and merger in dwarf galaxies
• Dwarf galaxies in the MATLAS Survey: Hubble Space Telescope observations of nuclear star clusters
• Galaxy mass dependence of metal-enrichment of nuclear star clusters
• Intermediate Mass Black Hole Binary Evolution in Nuclear Star Clusters: the effect of the stellar mass black hole population
• Evidence for Environmental Stripping in the Coma Cluster
• The Nuclear Star Cluster of M 74: a fossil record of the very early stages of a star-forming galaxy