An Intermediate-Mass Black Hole in the Globular Cluster G1: Improved Significance from New Keck and Hubble Space Telescope Observations

By K. Gebhardt, R. Rich, Luis C. Ho. 2005

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We present dynamical models for the massive globular cluster G1. The goal is to measure or place a significant upper limit on the mass of any central black hole. Whether or not globular clusters contain central massive black holes has important consequences for a variety of studies. We use new kinematic data obtained with Keck and new photometry from the Hubble Space Telescope (HST). The Keck spectra allow us to obtain kinematics out to large radii that are required to pin down the mass-to-light ratio of the dynamical model and the orbital structure. The HST observations give us a factor of 2 better spatial resolution for the surface brightness profile. By fitting nonparametric, spherical, isotropic models, we find a best-fit black hole mass of 1.7(±0.3) × 104 M☉. Fully general axisymmetric orbit-based models give similar results, with a black hole mass of 1.8(±0.5) × 104 M☉. The no-black-hole model has Δχ2 = 5 (marginalized over mass-to-light ratio), implying less than 3% significance. We have taken into account any change in the mass-to-light ratio in the center due to stellar remnants. These results are consistent with our previous estimate and inconsistent with the analysis of Baumgardt et al., who claim that G1 does not show evidence for a black hole. These new results make G1 the best example of a cluster that contains an intermediate-mass black hole.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/65976d5f0625a993e4545d19c799b01bc72cd92b

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Citations in the corpus

A New Sample of Low-Mass Black Holes in Active Galaxies (2007, background): “On the other hand, the M31 globular cluster G1 shows dynamical and radiative evidence for a central BH (Gebhardt et al. 2002, 2005; Pooley & Rappaport 2006; Ulvestad et al. 2007).”
The Mass Function of Active Black Holes in the Local Universe (2007, background): “On the other hand, the massive globular cluster G1 in Andromeda hosts a BH in accord with the MBH − σ∗ relation (Gebhardt et al. 2002, 2005), and NGC 4395, POX 52, and the Greene & Ho (2004) sample, all latetype galaxies hosting BHs with masses< 106 M⊙, are consistent with the low-mass…”
NEW LIMITS ON AN INTERMEDIATE-MASS BLACK HOLE IN OMEGA CENTAURI. II. DYNAMICAL MODELS (2009, methodology): “Gebhardt et al. (2002, 2005) used the velocity dispersion measured from integrated light near the center of the M31 cluster G1 to argue for the presence of a (1.8 ± 0.5) × 104 M⊙ dark mass at the cluster center.”
TIDAL DISRUPTION AND IGNITION OF WHITE DWARFS BY MODERATELY MASSIVE BLACK HOLES (2008, background): “…tens of kiloparsecs, a number of globular clusters (Brodie & Strader 2006; Moehler & Bono 2008) have a high enough central density to let white dwarfs interact and collide with other stars, or, if developed, with a central massive black hole (Gerssen et al. 2002, 2003; Gebhardt et al. 2002, 2005).”
Hubble Space Telescope STIS Spectra of Nuclear Star Clusters in Spiral Galaxies: Dependence of Age and Mass on Hubble Type (2006, background): “Also, the globular cluster G1 which could have an intermediate-mass BH (e.g., Gebhardt et al. 2002, 2005) has been suggested to have been the NC of a (now disrupted) dwarf galaxy.”
Binary Mergers and Growth of Black Holes in Dense Star Clusters (2005, background): “…et al. (2003a, 2003b) suggest that the observations of M15 and G1 and, in general, the properties of all core-collapsed clusters could be explained equally well by the presence of many compact stars near the center without a massive BH (see, e.g., van der Marel 2004; Gebhardt et al. 2005).”
Ultraluminous X-ray sources in the Chandra and XMM-Newton era (2011, background): “Dynamical evidence for IMBHs with masses∼ 104M⊙ has been proposed for a few globular clusters,e.g., G1 in M31 (Gebhardt et al. 2005), although the issue is still controversial (Anderson & van der Marel 2010).”
THE NGC 404 NUCLEUS: STAR CLUSTER AND POSSIBLE INTERMEDIATE-MASS BLACK HOLE (2010, background): “Possible IMBHs at the center of star clusters (and possible former nuclei) G1 (Gebhardt et al. 2005), ω Cen (Noyola et al. 2008; van der Marel & Anderson 2009), and M54 (Ibata et al. 2009) suggest that IMBHs with masses of 104−5 M⊙ may be widespread, but these results remain controversial.”
Black Holes in Pseudobulges and Spheroidals: A Change in the Black Hole-Bulge Scaling Relations at Low Mass (2008, background): “…Better statistics are needed, particularly since a fraction of ourmeasurements are probably dominated by rotation, but it is at least intriguing that the MBH- relation seems to be preserved, even for the massive globular clusters G1 and Omega Cen (Gebhardt et al. 2002, 2005; Noyola et al. 2008).”
The Coincidence of Nuclear Star Clusters and Active Galactic Nuclei (2008, background): “The globular cluster mass is 8 × 106 M⊙ (Baumgardt et al. 2003) and the black hole mass 1.8 × 104 M⊙(Gebhardt et al. 2005), giving MBH/MNC ∼ 2 × 10 −3.”
A Compact Supermassive Binary Black Hole System (2006, background): “There is also some evidence for intermediate-mass black holes, those with masses of a few hundred to a few thousand solar masses (see Filippenko & Ho 2003; Gebhardt et al. 2005).”