The Coincidence of Nuclear Star Clusters and Active Galactic Nuclei

By Anil Seth, M. Agüeros, Duane M. Lee, A. Basu-Zych. 2008

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We study galaxies that host both nuclear star clusters and AGNs, implying the presence of a massive black hole. We select a sample of 176 galaxies with previously detected nuclear star clusters that range from ellipticals to late-type spirals. We search for AGNs in this sample using optical spectroscopy and archival radio and X-ray data. We find galaxies of all Hubble types and with a wide range of masses (109-1011 M☉) hosting both AGNs and nuclear star clusters. From the optical spectra, we classify 10% of the galaxies as AGN and an additional 15% as composite, indicating a mix of AGN and star formation spectra. The fraction of nucleated galaxies with AGNs increases strongly as a function of galaxy and nuclear star cluster mass. For galaxies with both a nuclear star cluster and a black hole, we find that the masses of these two objects are quite similar. However, nondetections of black holes in Local Group nuclear star clusters show that not all clusters host black holes of similar masses. We discuss the implications of our results for the formation of nuclear star clusters and massive black holes.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/b5d9f72c484e963afa67453197704e50f2acd95b

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Citations in the corpus

Nuclear star clusters (2009, methodology): “However, there are a number of cases where nuclear star clusters and massive black holes are found to co-exist (Filippenko and Ho 2003; Seth et al. 2008a; Graham and Spitler 2009; Neumayer and Walcher 2012; Nguyen et al. 2019).”
The old Nuclear Star Cluster in the Milky Way (2014, background): “Estimates from stellar orbits show that the SMBH mass is M• = (4.31 ± 0.36) × 106M⊙ (Schödel et al. 2002; Ghez et al. 2008; Gillessen et al. 2009).”
THE NGC 404 NUCLEUS: STAR CLUSTER AND POSSIBLE INTERMEDIATE-MASS BLACK HOLE (2010, methodology): “Using data collected in Seth et al. (2008a), we plot the size and mass of clusters in Fig.”
THE NEXT GENERATION VIRGO CLUSTER SURVEY (NGVS). I. INTRODUCTION TO THE SURVEY (2012, background): “…X-ray, mid-IR, and radio wavelengths will make it possible to explore further the relationship between nuclei and SMBHs (e.g., Decarli et al. 2007; Seth et al. 2008; see also Volonteri et al. 2008), building upon what has been done to date for ACSVCS galaxies (e.g., Gallo et al. 2008, 2010;…”
An expanded Mbh–σ diagram, and a new calibration of active galactic nuclei masses (2010, background): “Nuclear star clusters (Ferrarese et al. 2006; Wehner & Harris 2006) are now known to co-exist with SMBHs at the centres of lowand intermediate-mass spheroids (Filippenko & Ho 2003; Graham & Driver 2007a; González Delgado et al. 2008; Seth et al. 2008; Graham & Spitler 2009).”
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.”
CO-EVOLUTION OF GALACTIC NUCLEI AND GLOBULAR CLUSTER SYSTEMS (2013, background): “The compilations of data for nearby galaxies by Seth et al. (2008) and Scott & Graham (2013) both have lower median valuesMNSC/M∗ ≈ 0.002, and a scaling MNSC ∝ σ2.”
Quantifying the coexistence of massive black holes and dense nuclear star clusters (2009, methodology): “To investigate this near dichotomy in the type of central massive object which galaxies house, Seth et al. (2008) searched for evidence of active galactic nuclei (AGN), and thus massive BHs, in galaxies with known NCs. Gonzalez ⋆ AGraham@astro.swin.edu.au Delgado et al. (2008) simultaneously…”
Greatly Enhanced Merger Rates of Compact-object Binaries in Non-spherical Nuclear Star Clusters (2017, background): “Examples of galaxies hosting both a compact NC and an AGN are known across a wide range of galaxy masses (Seth et al. 2008; Neumayer & Walcher 2012), suggesting that NCs and MBHs often co-exist in galaxies.”
Black hole growth through hierarchical black hole mergers in dense star clusters: implications for gravitational wave detections (2018, result): “…by observations, we leave it as a parameter in our calculations below, but note that values of fBH & 0.5 are consistent with the results of galaxy formation models (Antonini et al. 2015), while observations prefer marginally smaller values fBH ∼ 0.2 (Seth et al. 2008; Nguyen et al. 2018).”
NEW LIMITS ON AN INTERMEDIATE-MASS BLACK HOLE IN OMEGA CENTAURI. II. DYNAMICAL MODELS (2009, background): “Accretion activity is known to exist in at least some of these nuclei (e.g., Seth et al. 2008).”
Nuclear Activity in Nearby Galaxies (2008, background): “Nuclear star clusters do not appear to directly impact a galaxy’s ability to host an AGN (Seth et al. 2008).”
Doing Science with eLISA: Astrophysics and Cosmology in the Millihertz Regime (2012, background): “…et al., 2011a,b, Kuo et al., 2011, Xiao et al., 2011) and evidence exists that some of these low mass black holes of M 105 M cohabit 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).”
The nuclear star cluster of the Milky Way: proper motions and mass (2009, background): “Most NSCs contain a mixed stellar population with signs of repeated episodes of star formation (Walcher et al. 2006).”
Pathways to massive black holes and compact star clusters in pre-galactic dark matter haloes with virial temperatures ≳10 000 K (2008, unknown): “…of the gas in our simulations is compared to observed astrophysical objects we also show the typical masses and radii of observed compact nuclear star clusters, globular c© 0000 RAS, MNRAS 000, 000–000 clusters, and dwarf galaxies (Belokurov et al. 2007; Merritt 2008; Seth et al. 2008).”
THE MBH–LSPHEROID RELATION AT HIGH AND LOW MASSES, THE QUADRATIC GROWTH OF BLACK HOLES, AND INTERMEDIATE-MASS BLACK HOLE CANDIDATES (2012, background): “The bulge of the Scd galaxy NGC 1042 has a dust corrected magnitude of −19.13 ± 0.75 K-mag (Knapen et al. 2003; Graham &Worley 2008) and houses an active black hole (Shields et al. 2008; Seth et al. 2008).”
Masses and scaling relations for nuclear star clusters, and their co-existence with central black holes (2016, unknown): “Our approach to derive MNSC in latetype hosts is similar to that in Seth et al. (2008a) who find good agreement between photometric and dynamical mass estimates to within a factor of two, which is comparable to the mass uncertainties calculated here.”
Surface brightness profile of the Milky Way’s nuclear star cluster (2014, background): “On the other hand, the discs or rings observed by Seth et al. (2006) and Seth et al. (2008b) may be more like the nuclear stellar disc (NSD) of ∼200 pc radius in which the MWNSC is embedded (Launhardt et al. 2002).”
MERGING BLACK HOLE BINARIES IN GALACTIC NUCLEI: IMPLICATIONS FOR ADVANCED-LIGO DETECTIONS (2016, background): “This is certainly not the case for at least a handful of NSCs which are known to have MBHs at their center (e.g., Seth et al. 2008).”