Henize 2–10: The Ongoing Formation of a Nuclear Star Cluster Around a Massive Black Hole

Abstract

The central region of the galaxy Henize 2-10 hosts a black hole (BH) candidate with a mass Log (M BH /M ⊙ ) = 6.3 ± 1.1. While this putative black hole does not appear to coincide with any central stellar overdensity, it is surrounded by 11 young massive clusters with masses above 10 5 M ⊙ . The availability of high quality data on the structure of the galaxy and the age and mass of the clusters provides excellent initial conditions for studying the dynamical evolution of Henize 2-10's nucleus.Here we present a set of N -body simulations in which we model the future evolution of the central clusters and the black hole to understand whether and how they will merge to form a nuclear star cluster. Nuclear star clusters (NSCs) are present in a majority of galaxies with stellar mass similar to Henize 2-10. While the results depend on the choice of initial conditions, we find that a NSC with mass M NSC ≃ 4 − 6 × 10 6 M ⊙ and effective radius r NSC ≃ 2.6 − 4.1 pc will form within 0.2 Gyr. This work is the first showing, in a realistic realization of the host galaxy and its star cluster system, that the formation of a bright nucleus is a process that can happen after the formation of a central massive BH leading to a composite NSC+BH central system. The cluster merging process does not significantly affect the kinematics of the BH; when a stationary state is reached its position changes by 1 pc and its velocity by < 2 km s −1 .

The MEGaN project – I. Missing formation of massive nuclear clusters and tidal disruption events by star clusters–massive black hole interactions

“…Observationally, a NSC in a galactic nucleus is identified as an evident edge in the host galaxy surface brightness profile Turner et al 2012;Georgiev & Böker 2014;Arca-Sedda et al 2015). However, we did not found any evident edge neither in our model surface density profile, nor in the projected radial velocity profile, which is shown in Fig.…”

“…Moreover, the inspiralling and merger of GCs in a galaxy has found a significant support by very recent finding of RR Lyrae stars in the centre of our Galaxy (Minniti et al 2016) Using observational data of the dwarf starburst galaxy Henize 2-10, which hosts an SMBH surrounded by 11 massive clusters (Reines & Deller 2012;Nguyen et al 2014), Arca-Sedda et al (2015) have shown that the formation of a NSC is regulated by the gravitational galactic field and the SMBH, and it can occur on relatively short time-scales, < 1 Gyr. Since the Henize 2-10 clusters are young, with ages ∼ 5 Myr (Chandar et al 2003), these results suggest that NSCs can form on time scales compatible with the SMBH growth.…”

Birth, Life, and Death of Black Hole Binaries around Supermassive Black Holes: Dynamical Evolution of Gravitational Wave Sources

“…being τ 0 a normalization factor, g(e GC , γ) a weak function of the cluster eccentricity and the galaxy slope, α = −0.67 and β = 1.76 (see also Arca-Sedda et al 2015).…”

On the formation of compact, massive subsystems in stellar clusters and its relation with intermediate-mass black holes

“…This mechanism, called dynamical friction (df), arises directly from two-body encounters and plays a significant role in shaping the evolution of astrophysical systems on very different scales (Bekenstein 1973;Tremaine 1976;Capuzzo-Dolcetta 1993;Milosavljević & Merritt 2001;Gualandris & Merritt 2008;Antonini 2013;Arca-Sedda & Capuzzo-Dolcetta 2014b;Arca-Sedda et al 2015).…”