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

Cited by in corpus (15)

• Reconstructing the Disrupted Dwarf Galaxy $Gaia$-Sausage/Enceladus Using its Stars and Globular Clusters
• Clues to the formation of Liller 1 from modeling its complex star formation history
• Kinematic differences between multiple populations in Galactic globular clusters
• 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
• 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
• Is Terzan 5 the remnant of a building block of the Galactic bulge? Evidence from APOGEE
• Two Luminous Post-AGB Stars in the Galactic Globular Cluster M19
• 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
• 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
• Star Cluster Ecology: Revisiting the Origin of Iron and Age Complex Clusters