DISSIPATIONLESS FORMATION AND EVOLUTION OF THE MILKY WAY NUCLEAR STAR CLUSTER

By F. Antonini, R. Capuzzo-Dolcetta, A. Mastrobuono-Battisti, D. Merritt. 2011

145 citations recorded by the source corpus.

In one widely discussed model for the formation of nuclear star clusters (NSCs), massive globular clusters spiral into the center of a galaxy and merge to form the nucleus. It is now known that at least some NSCs coexist with supermassive black holes (SMBHs); this is the case, for instance, in the Milky Way. In this paper, we investigate how the presence of an SMBH at the center of the Milky Way impacts the merger hypothesis for the formation of its NSC. Starting from a model consisting of a low-density nuclear stellar disk and the SMBH, we use direct N-body simulations to follow the successive inspiral and merger of globular clusters. The clusters are started on circular orbits of radius 20 pc, and their initial masses and radii are set up in such a way as to be consistent with the galactic tidal field at that radius. These clusters, decayed orbitally in the central region due to their large mass, were followed in their inspiral events; as a result, the total accumulated mass by ≈10 clusters is about 1.5 × 107 M☉. Each cluster is disrupted by the SMBH at a distance of roughly 1 pc. The density profile that results after the final inspiral event is characterized by a core of roughly this radius and an envelope with density that falls off ρ ∼ r−2. These properties are similar to those of the Milky Way NSC, with the exception of the core size, which in the Milky Way is somewhat smaller. But by continuing the evolution of the model after the final inspiral event, we find that the core shrinks substantially via gravitational encounters in a time (when scaled to the Milky Way) of 10 Gyr as the stellar distribution evolves toward a Bahcall–Wolf cusp. We also show that the luminosity function of the Milky Way NSC is consistent with the hypothesis that 1/2 of the mass comes from old (∼10 Gyr) stars, brought in by globular clusters, with the other half due to continuous star formation. We conclude that a model in which a large fraction of the mass of the Milky Way NSC is due to infalling globular clusters is consistent with existing observational constraints.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/bfa31da23bf1f7cb98f57b3c2234d5ba1f52796c

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Instrumentation

Citations in the corpus

The old Nuclear Star Cluster in the Milky Way (2014, background): “In the simulations of Antonini et al. (2012), the final relaxed model has an inner slope of γ = 0.45, not far from our models.”
Mean proper motions, space orbits, and velocity dispersion profiles of Galactic globular clusters derived fromGaiaDR2 data (2018, background): “…cluster population in the inner parts is most likely just a small portion of the initial population, with the other clusters having either dissolved by the strong tidal field or spiraled into the centre of the Milky Way and merged with the nuclear cluster of the Milky Way (Antonini et al. 2012).”
Surface brightness profile of the Milky Way’s nuclear star cluster (2014, background): “Thus, extinction would naturally lead to finding a more flattened NSD around the MWNSC.”
CO-EVOLUTION OF GALACTIC NUCLEI AND GLOBULAR CLUSTER SYSTEMS (2013, background): “…Department of Astronomy & Astrophysics, New York, NY 10027 4 Institute for Advanced Study, Princeton, NJ 08540 Capuzzo-Dolcetta & Miocchi (2008), Antonini et al. (2012), and Antonini (2013) have explored cluster inspiral and disruption leading to the formation of a NSC. Major uncertainties in…”
Masses and scaling relations for nuclear star clusters, and their co-existence with central black holes (2016, unknown): “…by a NSC, the structure and integrity of the NSC will be impacted if the MBH mass is a sufficiently high fraction of the bound NSC mass (e.g. Antonini et al. 2012, 2015; Antonini 2013, see also refs. in § 3.3) In massive globular clusters (GCs) and ultra compact dwarf galaxies (UCDs), the…”
The Galaxy in Context: Structural, Kinematic, and Integrated Properties (2016, background): “There are indications for a local kinematic misalignment in the LOS velocities but not in the PMs (Feldmeier et al. 2014, Fritz et al. 2016), which, if confirmed, might indicate some contribution to the NSC mass by infalling star clusters (Antonini et al. 2012); this needs further study.”
Nuclear star clusters (2009, methodology): “Apart from the aforementioned work of Hartmann et al. (2011) and Antonini et al. (2012) who argue that both formation mechanisms are required to replicate observations of specific NSCs, the only theoretical effort to tackle this problem has been the semi-analytic model of Antonini et al. (2015).”