Quantifying the coexistence of massive black holes and dense nuclear star clusters

By Alister W. Graham, Lee R. Spitler. 2009

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In large spheroidal stellar systems, such as elliptical galaxies, one invariably finds a 10 6 -10 9 M ⊙ supermassive black hole at their centre. In contrast, within dwarf elliptical galaxies one predominantly observes a 10 5_ 10 7 M ⊙ nuclear star cluster. To date, few galaxies have been found with both types of nuclei coexisting and even less have had the masses determined for both central components. Here, we identify one dozen galaxies housing nuclear star clusters and supermassive black holes whose masses have been measured. This doubles the known number of such hermaphrodite nuclei - which are expected to be fruitful sources of gravitational radiation. Over the host spheroid (stellar) mass range 10 8_ 10 11 M ⊙ , we find that a galaxy's nucleus-to-spheroid (baryon) mass ratio is not a constant value but decreases from a few per cent to ~0.3 per cent such that log[(M BH + M NC )/M sph ] = -(0.39 ± 0.07) Iog[M sph /10 10 M ⊙ ] ― (2.18 ± 0.07). Once dry merging commences and the nuclear star clusters disappear, this ratio is expected to become a constant value. As a byproduct of our investigation, we have found that the projected flux from resolved nuclear star clusters is well approximated with Sersic functions having a range of indices from ~0.5 to ~3, the latter index describing the Milky Way's nuclear star cluster.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/77ba5c57b51626508f4452f31403d14f15a9a8d2

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Citations in the corpus

THE MBH–LSPHEROID RELATION AT HIGH AND LOW MASSES, THE QUADRATIC GROWTH OF BLACK HOLES, AND INTERMEDIATE-MASS BLACK HOLE CANDIDATES (2012, background): “…assuming that this galaxy’s excess nuclear light was due to an AGN rather than a massive nuclear disk and dense star cluster (Balcells et al. 2007; Graham & Spitler 2009), and the exclusion of the Sc galaxy NGC 2748 due to potential dust complications with its estimated black hole mass (Atkinson…”
DISSIPATIONLESS FORMATION AND EVOLUTION OF THE MILKY WAY NUCLEAR STAR CLUSTER (2011, background): “A handful of other galaxies are also known to contain both a NSC and a SMBH (Seth et al. 2008; Graham & Spitler 2009), and the ratio of SMBH to NSC mass in these galaxies is of order unity.”
THE NGC 404 NUCLEUS: STAR CLUSTER AND POSSIBLE INTERMEDIATE-MASS BLACK HOLE (2010, methodology): “These parameters are in the ranges typical of NSCs (Côté et al. 2006; Graham & Spitler 2009) in other galaxies.”
The Spitzer/IRAC view of black hole–bulge scaling relations (2010, background): “Moreover Graham & Spitler (2009) derive a linear regression between the nuclear mass (BH plus NSC) and the stellar mass of the host spheroid.”
Masses and scaling relations for nuclear star clusters, and their co-existence with central black holes (2016, unknown): “Subsequently, Graham & Spitler (2009) also included data for coexisting NSCs and MBHs in early-types, but they considered the fractional mass ratioMBH/(MNSC+MBH) against host spheroid mass. Neumayer & Walcher (2012), whose data we 10 4 10 5 10 6 10 7 10 8 10 9 10 10 10 7 10 8 10 9 10 10 10 11 10 12…”
On the rate of black hole binary mergers in galactic nuclei due to dynamical hardening (2017, background): “Galactic nuclei have stellar densities that can reach ∼ 107 M⊙ pc−3 (Graham & Spitler 2009), inside some of the deepest grav- itational potentials in the Universe.”
Doing Science with eLISA: Astrophysics and Cosmology in the Millihertz Regime (2012, background): “ 2011, Xiao et al., 2011) and evidence exists that some of these low mass black holes of M <105 Mcohabit nuclear star clusters (Barth et al., 2009, Bekki and Graham, 2010, Ferrarese et al., 2006, Graham and Spitler, 2009, Seth et al., 2008, Wehner and Harris, 2006). Dwarf galaxies in the galactic”
An expanded Mbh–σ diagram, and a new calibration of active galactic nuclei masses (2010, methodology): “8 explores the speculation by Graham & Spitler (2009) that an insightful quantity to plot on the vertical axis may be the combination of the SMBH plus the nuclear star cluster mass. Nayakshin, Wilkinson & King (2009) discuss how competing feedback from a SMBH and a nuclear star cluster may explain…”
Surface brightness profile of the Milky Way’s nuclear star cluster (2014, methodology): “NSCs show complex morphologies and can coexist with massive black holes (MBHs; Seth et al. 2008b; Graham & Spitler 2009; Neumayer & Walcher 2012).”
Nuclear star clusters (2009, methodology): “…light excess by Kormendy 3 A corresponding result for NSC candidates in low-mass dwarf galaxies was pointed out by Georgiev et al. (2009). et al. (2009), but Graham and Spitler (2009) classify it as an NSC with an effective radius of 6 pc, well within the distribution of sizes of typical NSCs.”