Central kinematics of the globular cluster NGC 2808: upper limit on the mass of an intermediate-mass black hole

Lützgendorf, Nora; Kissler-Patig, M.; Gebhardt, Karl; Baumgardt, Holger; Noyola, Eva; Jalali, B.; Zeeuw, P. T. de; Neumayer, Nadine

doi:10.1051/0004-6361/201219375

Cited by 37 publications

(52 citation statements)

References 60 publications

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“…For more details on the observations and reductions we refer to Lützgendorf et al (2012). From these data we construct a velocity map which is shown in Fig.…”

Section: Radial Velocitiesmentioning

confidence: 99%

“…The two fast stars are visible as bright "blue" spots and are labeled with FS1 and FS2 in the maps. To estimate their velocities, we use the output of a shot noise routine described in Lützgendorf et al (2012). This routine computes for every spaxel the number of stars that contribute to the light of the spaxel and indicates which spaxels are dominated by a single star.…”

Section: Radial Velocitiesmentioning

confidence: 99%

“…With this information we find the spaxel to which our two (bright) fast stars contribute with more than 80% of the light and use the radial velocities derived for these spaxels as the ones of the stars. These velocities are corrected for the systemic velocity of the cluster (V r = 93.6 km s −1 , Lützgendorf et al 2012).…”

Section: Radial Velocitiesmentioning

confidence: 99%

“…We obtain an escape velocity profile by parametrizing our surface-brightness profile with a multi-gaussian expansion (MGE, Emsellem et al 1994) as implemented in the Jeans anisotropic models (JAM) by Cappellari (2008). The parametrization allows an easy way of deprojecting the profile after multiplying it with the derived M/L profile from our kinematic fits (see Lützgendorf et al 2012). The gravitational potential generated by the deprojected density of stars is given by Eq.…”

Section: Radial Velocitiesmentioning

confidence: 99%

“…By analyzing Fabry-Perot data, Gebhardt et al (2012) found rotation in the outer parts of the cluster with a maximum rotation velocity of V rot ∼ 5 km s −1 . The latest radial velocity measurements of the cluster core by Lützgendorf et al (2012) have shown that NGC 2808 most probably does not host an intermediate-mass black hole: the best fit model is consistent with no IMBH and gives an upper limit of M BH < 1 × 10 4 M .…”

Section: Introductionmentioning

confidence: 95%

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High-velocity stars in the cores of globular clusters: the illustrative case of NGC 2808

Lützgendorf

Gualandris

Kissler-Patig

et al. 2012

A&A

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Context. We report the detection of five high-velocity stars in the core of the globular cluster NGC 2808. The stars lie on the red giant branch and show total velocities between 40 and 45 km s −1 . For a core velocity dispersion σ c = 13.4 km s −1 , this corresponds to up to 3.4σ c . These velocities are close to the estimated escape velocity (∼50 km s −1 ) and suggest an ejection from the core. Two of these stars have been confirmed in our recent integral field spectroscopy data and we will discuss them in more detail here. These two red giants are located at a projected distance of ∼0.3 pc from the center. According to their positions on the color magnitude diagram, both stars are cluster members. Aims. We investigate several possible origins for the high velocities of the stars and conceivable ejection mechanisms. Since the velocities are close to the escape velocity, it is not obvious whether the stars are bound or unbound to the cluster. We therefore consider both cases in our analysis. Methods. We perform numerical simulations of three-body dynamical encounters between binaries and single stars and compare the resulting velocity distributions of escapers with the velocities of our stars. If the stars are bound, the encounters must have taken place when the stars were still on the main sequence. We compare the predictions for a single dynamical encounter with a compact object with those of a sequence of two-body encounters due to relaxation. If the stars are unbound, the encounter must have taken place recently, when the stars were already in the giant phase. Results. After including binary fractions and black-hole retention fractions, projection effects, and detection probabilities from Monte-Carlo simulations, we estimate the expected numbers of detections for all the different scenarios. Based on these numbers, we conclude that the most likely scenario is that the stars are bound and were accelerated by a single encounter between a binary of main-sequence stars and a ∼10 M black hole. Finally, we discuss the origin of previously discovered fast stars in globular clusters, and conclude that the case of NGC 2808 is most likely a representative case for most other detections of fast stars in globular clusters. We show that with the present analysis we are able to explain high-velocity stars in the clusters M3 and 47 Tucanae with simple dynamical encounters.

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“…For more details on the observations and reductions we refer to Lützgendorf et al (2012). From these data we construct a velocity map which is shown in Fig.…”

Section: Radial Velocitiesmentioning

confidence: 99%

Section: Radial Velocitiesmentioning

confidence: 99%

Section: Radial Velocitiesmentioning

confidence: 99%

Section: Radial Velocitiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 95%

See 3 more Smart Citations

High-velocity stars in the cores of globular clusters: the illustrative case of NGC 2808

Lützgendorf

Gualandris

Kissler-Patig

et al. 2012

A&A

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A study of 137 intermediate mass black hole candidates

Ter-Kazarian

Shidhani²

2019

Astrophys Space Sci

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The nuclear cluster of the Milky Way: total mass and luminosity

et al. 2013

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Here we present the fundamental properties of the nuclear cluster of the Milky Way. First, we derive its structural properties by constructing a density map of the central 1000 using extinction-corrected star counts. We can describe the data with a two-component model built from Sersic profiles. The inner nearly spherical component is the nuclear cluster. The outer, strongly flattened component can be identified with the stellar component of the circumnuclear zone. Second, we enlarge the radius inside which detailed dynamics are available from 1 pc to 4 pc. We use more than 10000 individual proper motions and more than 2700 radial velocities. We determine the cluster mass by means of isotropic spherical Jeans modeling. We get a nuclear cluster mass within 100 of M 100 = (6.11 ± 0.52| fi xR 0 ± 0.97|R 0 ) × 10 6 M , which corresponds to a total cluster mass of MNC = (13.08 ± 2.51| fi xR 0 ± 2.08|R 0 ) × 10 6 M . By combination of our mass with the flux we calculate M/L = 0.50 ± 0.12M /L ,K s for the central 100 . That is broadly consistent with a Chabrier IMF. With its mass and a luminosity of MK s = −15.30±0.26 the nuclear cluster is a bright and massive specimen with a typical size.

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Central kinematics of the globular cluster NGC 2808: upper limit on the mass of an intermediate-mass black hole

Cited by 37 publications

References 60 publications

High-velocity stars in the cores of globular clusters: the illustrative case of NGC 2808

High-velocity stars in the cores of globular clusters: the illustrative case of NGC 2808

A study of 137 intermediate mass black hole candidates

The nuclear cluster of the Milky Way: total mass and luminosity

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