The Accreted Nuclear Clusters of the Milky Way

Abstract

A number of the massive clusters in the halo, bulge and disc of the Galaxy are not genuine globular clusters (GCs), but instead are different beasts altogether. They are the remnant nuclear star clusters (NSCs) of ancient galaxies since accreted by the Milky Way. While some clusters are readily identifiable as NSCs, and can be readily traced back to their host galaxy (e.g., M54 and the Sagittarius Dwarf galaxy) others have proven more elusive. Here we combine a number of independent constraints, focusing on their internal abundances and overall kinematics, to find NSCs accreted by the Galaxy and trace them to their accretion event. We find that the true NSCs accreted by the Galaxy are: M54 from the Sagittarius Dwarf, $\omega$ Centari from Gaia-Enceladus/Sausage, NGC 6273 from Kraken and (potentially) NGC 6934 from the Helmi Streams. These NSCs are prime candidates for searches of intermediate mass black holes (BHs) within star clusters, given the common occurrence of galaxies hosting both NSCs and central massive BHs. No NSC appears to be associated with Sequoia or other minor accretion events. Other claimed NSCs are shown not to be such. We also discuss the peculiar case of Terzan 5, which may represent a unique case of a cluster-cluster merger.

11 pages, accepted for publication in MNRAS

References in corpus (47)

• The mass distribution and gravitational potential of the Milky Way
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. I. Overview of the Project and Detection of Multiple Stellar Populations
• Evidence for Two Early Accretion Events That Built the Milky Way Stellar Halo
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. IX. The Atlas of Multiple Stellar Populations
• The ACS Survey of Galactic Globular Clusters. III. The Double Subgiant Branch of NGC 1851
• A Supermassive Black Hole in an Ultracompact Dwarf Galaxy
• Gemini and Hubble Space Telescope Evidence for an Intermediate Mass Black Hole in omega Centauri
• The nucleus of the Sagittarius dSph galaxy and M54: a window on the process of galaxy nucleation
• N-body modeling of globular clusters: Masses, mass-to-light ratios and intermediate-mass black holes
• A massive cluster of Red Supergiants at the base of the Scutum-Crux arm
• Reconstructing the star formation history of the Milky Way disc(s) from chemical abundances
• An abundance analysis of bright giants in the globular cluster NGC 1851
• Clues to Nuclear Star Cluster Formation from Edge-on Spirals
• Reverse engineering the Milky Way
• Iron and s-elements abundance variations in NGC5286: comparison with anomalous globular clusters and Milky Way satellites
• Iron and neutron-capture element abundance variations in the globular cluster M2 (NGC 7089)
• The E-MOSAICS project: tracing galaxy formation and assembly with the age-metallicity distribution of globular clusters
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. II. The seven stellar populations of NGC7089 (M2)
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XIX. A Chemical Tagging of the Multiple Stellar Populations Over the Chromosome Maps
• Age as a Major Factor in the Onset of Multiple Populations in Stellar Clusters
• Weighing the stellar constituents of the Galactic halo with APOGEE red giant stars
• Contribution of stripped nuclear clusters to globular cluster and ultra-compact dwarf galaxy populations
• Origin of the excess of high-energy retrograde stars in the Galactic halo
• The Chemical Compositions of Accreted and {\it in situ} Galactic Globular Clusters According to SDSS/APOGEE
• Multiple populations in globular clusters and their parent galaxies
• Ceci n'est pas a globular cluster: the metallicity distribution of the stellar system Terzan 5
• KMOS view of the Galactic Centre - II. Metallicity distribution of late-type stars
• Density and kinematic cusps in M54 at the heart of the Sagittarius dwarf galaxy: evidence for a 10^4 M_sun Black Hole?
• CNO abundances in the globular clusters NGC 1851 and NGC 6752
• The age of the young bulge-like population in the stellar system Terzan5: linking the Galactic bulge to the high-z Universe
• Na-O Anticorrelation and HB. VI. The chemical composition of the peculiar bulge globular cluster NGC 6388
• The Outer Envelopes of Globular Clusters. II. NGC 1851, NGC 5824 and NGC 1261
• 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
• The halo+cluster system of the Galactic globular cluster NGC1851
• An old, metal-poor globular cluster in Sextans A and the metallicity floor of globular cluster systems
• The Relationship Between Globular Cluster Mass, Metallicity, and Light Element Abundance Variations
• The origin of the spurious iron spread in the globular cluster NGC 3201
• Tails and streams around the Galactic globular clusters NGC1851, NGC1904, NGC2298 and NGC2808
• The minimum metallicity of globular clusters and its physical origin -- implications for the galaxy mass-metallicity relation and observations of proto-globular clusters at high redshift
• The Most Metal-poor Stars in Omega Centauri (NGC 5139)
• The Discovery of a Massive Cluster of Red Supergiants with GLIMPSE
• A broad perspective on multiple abundance populations in the globular cluster NGC 1851
• Lost and found: evidence of Second Generation stars along the Asymptotic Giant Branch of the globular cluster NGC 6752
• Light and Heavy Element Abundance Variations in the Outer Halo Globular Cluster NGC 6229
• Light element variations within the different age-metallicity populations in the nucleus of the Sagittarius dwarf
• NGC 6388 reloaded: some like it hot, but not too much

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• Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia EDR3 stars brighter than G=18.5
• The chemical characterisation of halo substructure in the Milky Way based on APOGEE
• Fast-moving stars around an intermediate-mass black hole in Omega Centauri
• Reconstructing the Disrupted Dwarf Galaxy $Gaia$-Sausage/Enceladus Using its Stars and Globular Clusters
• Evidence from Disrupted Halo Dwarfs that $r$-process Enrichment via Neutron Star Mergers is Delayed by $\gtrsim 500$ Myrs
• Detection of a $\sim$100,000 M${}_{\odot }$ black hole in M31's most massive globular cluster: A tidally stripped nucleus
• The complex stellar system M 22: confirming abundance variations with high precision differential measurements
• Clues to the formation of Liller 1 from modeling its complex star formation history
• Kinematic differences between multiple populations in Galactic globular clusters
• Classifying globular clusters and applying them to estimate the mass of the Milky Way
• oMEGACat III. Multi-band photometry and metallicities reveal spatially well-mixed populations within $\omega$ Centauri's half-light radius
• oMEGACat II -- Photometry and proper motions for 1.4 million stars in Omega Centauri and its rotation in the plane of the sky
• Orbits of globular clusters computed with dynamical friction in the Galactic anisotropic velocity dispersion field
• Peeking beneath the precision floor I: metallicity spreads and multiple elemental dispersions in the globular clusters NGC 288 and NGC 362
• 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
• Globular cluster metallicity distributions in the E-MOSAICS simulations
• Abundance ties: Nephele and the globular cluster population accreted with $\omega$ Cen. Based on APOGEE DR17 and Gaia EDR3
• A stellar census in globular clusters with MUSE. A new perspective on the multiple main sequences of $\omega$ Centauri
• Potential Black Hole Seeding of the Spiral Galaxy NGC 4424 via an Infalling Star Cluster
• SHOTGLAS II. MUSE spectroscopy of blue horizontal branch stars in the core of $\omega$ Centauri and NGC 6752
• The Dark Matter Halo of M54
• oMEGACat. VI. Analysis of the overall kinematics of Omega Centauri in 3D: velocity dispersion, kinematic distance, anisotropy, and energy equipartition
• Spatially Resolving the Star Formation Histories of Three Nearby Nuclear Star Clusters
• Chemodynamical study of two CEMP-no stars from the Hamburg/ESO Survey
• Is Terzan 5 the remnant of a building block of the Galactic bulge? Evidence from APOGEE
• Metallicity of the globular cluster NGC 6388 from high resolution spectra of more than 160 giant stars
• The Bulge Cluster Origin (BulCO) survey at the ESO-VLT: probing the early history of the Milky Way assembling. Design and first results in Liller1
• Trojan globular clusters: radial migration via trapping in bar resonances
• Globular Cluster Intrinsic Iron Abundance Spreads: II. Protocluster Metallicities and the Age-Metallicity Relations of Milky Way Progenitors
• On the manifest link between Terzan 5 and the Galactic bulge
• A stellar census in globular clusters with MUSE. Metallicity spread and dispersion among first-population stars
• Studying stellar populations in Omega Centauri with phylogenetics
• Dating N loud AGNs at high redshift: GS3073 as a snapshot of wCen like evolution of a nuclear star cluster
• Black Hole Scaling Relations in the Dwarf-galaxy Regime with $Gaia$-Sausage/Enceladus and $\omega$Centauri
• Two Luminous Post-AGB Stars in the Galactic Globular Cluster M19
• Kinematics of metallicity populations in Omega Centauri using Gaia Focused Product Release and Hubble Space Telescope
• CAPOS: The bulge Cluster APOgee Survey VIII. Final ASPCAP results for all clusters
• Bulge Fossil Fragments as a new population of factories of gravitational wave sources in the Galaxy
• Studying Binary Systems in Omega Centauri with MUSE. I. Detection of Spectroscopic Binaries
• Chemical tagging with APOGEE, MUSE, and HST: constraints on the formation of $\omega$ Centauri
• Probing populations of dark stellar remnants in the globular clusters 47 Tuc and Terzan 5 using pulsar timing
• A Search for Wandering Black Holes in the Milky Way with Gaia and DECaLS
• A population of luminous globular clusters and stripped nuclei with elevated mass to light ratios around NGC 5128
• Predicting Images for the Dynamics Of stellar Clusters (π-DOC): a deep learning framework to predict mass, distance and age of globular clusters
• Star Cluster Ecology: Revisiting the Origin of Iron and Age Complex Clusters
• Tracing Milky Way substructure with an RR Lyrae hierarchical clustering forest
• Resolved nuclear kinematics link the formation and growth of nuclear star clusters with the evolution of their early and late-type hosts
• A Pearl in the Shell: an ultra-compact dwarf within the tidal debris surrounding spiral galaxy NGC 7531