A Nonparametric Estimate of the Mass of the Central Black Hole in the Galaxy

Chakrabarty, Dalia; Saha, Prasenjit

doi:10.1086/321104

Cited by 36 publications

(43 citation statements)

References 22 publications

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“…Milky Way.-We use the black hole mass estimate by Chakrabarty & Saha (2001), ð1:8 þ0:4 À0:3 Þ Â 10 6 M . For comparison, Ghez et al (1998) find ð2:4 AE 0:2Þ Â 10 6 M , and find ð2:6 3:3Þ Â 10 6 M .…”

Section: Comments On Individual Galaxiesmentioning

confidence: 99%

The Slope of the Black Hole Mass versus Velocity Dispersion Correlation

Tremaine

Gebhardt

Bender³

et al. 2002

ApJ

2,481

166

3,186

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Observations of nearby galaxies reveal a strong correlation between the mass of the central dark object M BH and the velocity dispersion of the host galaxy, of the form logðM BH =M Þ ¼ þ logð = 0 Þ; however, published estimates of the slope span a wide range (3.75-5.3). Merritt & Ferrarese have argued that low slopes (d4) arise because of neglect of random measurement errors in the dispersions and an incorrect choice for the dispersion of the Milky Way Galaxy. We show that these explanations and several others account for at most a small part of the slope range. Instead, the range of slopes arises mostly because of systematic differences in the velocity dispersions used by different groups for the same galaxies. The origin of these differences remains unclear, but we suggest that one significant component of the difference results from Ferrarese & Merritt's extrapolation of central velocity dispersions to r e =8 (r e is the effective radius) using an empirical formula. Another component may arise from dispersion-dependent systematic errors in the measurements. A new determination of the slope using 31 galaxies yields ¼ 4:02 AE 0:32, ¼ 8:13 AE 0:06 for 0 ¼ 200 km s À1 . The M BH -relation has an intrinsic dispersion in log M BH that is no larger than 0.25-0.3 dex and may be smaller if observational errors have been underestimated. In an appendix, we present a simple kinematic model for the velocity-dispersion profile of the Galactic bulge.

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Section: Comments On Individual Galaxiesmentioning

confidence: 99%

The Slope of the Black Hole Mass versus Velocity Dispersion Correlation

Tremaine

Gebhardt

Bender³

et al. 2002

ApJ

2,481

166

3,186

View full text Add to dashboard Cite

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“…Ghez et al 1998;Genzel et al 2000;Chakrabarty & Saha 2001). Figer et al (2003) and Zhu et al (2008) have argued that this bias can be attributed to the low space density of late-type stars near Sgr A * .…”

Section: Moment Estimatorsmentioning

confidence: 99%

The nuclear star cluster of the Milky Way: proper motions and mass

Schödel¹,

Merritt²,

Eckart³

2009

A&A

247

350

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Context. Nuclear star clusters (NSCs) are located at the photometric and dynamical centers of the majority of galaxies. They are among the densest star clusters in the Universe. The NSC in the Milky Way is the only object of this class that can be resolved into individual stars. The massive black hole Sagittarius A* is located at the dynamical center of the Milky Way NSC. Aims. In this work we examine the proper motions of stars out to distances of 1.0 pc from Sgr A*. The aim is to examine the velocity structure of the MW NSC and acquire a reliable estimate of the stellar mass in the central parsec of the MW NSC, in addition to the well-known black hole mass. Methods. We use multi-epoch adaptive optics assisted near-infrared observations of the central parsec of the Galaxy obtained with NACO/CONICA at the ESO VLT. Stellar positions are measured via PSF fitting in the individual images and transformed into a common reference frame via suitable sets of reference stars. Results. We measured the proper motions of more than 6000 stars within ∼1.0 pc of Sagittarius A*. The full data set is provided in this work. We largely exclude the known early-type stars with their peculiar dynamical properties from the dynamical analysis. The cluster is found to rotate parallel to Galactic rotation, while the velocity dispersion appears isotropic (or anisotropy may be masked by the cluster rotation). The Keplerian fall-off of the velocity dispersion due to the point mass of Sgr A* is clearly detectable only at R < ∼ 0.3 pc. Nonparametric isotropic and anisotropic Jeans models are applied to the data. They imply a best-fit black hole mass of 3.6 +0.2 −0.4 × 10 6 M . Although this value is slightly lower than the current canonical value of 4.0 × 10 6 M , this is the first time that a proper motion analysis provides a mass for Sagittarius A* that is consistent with the mass inferred from orbits of individual stars. The point mass of Sagittarius A* is not sufficient to explain the velocity data. In addition to the black hole, the models require the presence of an extended mass of 0.5−1.5 × 10 6 M in the central parsec. This is the first time that the extended mass of the nuclear star cluster is unambiguously detected. The influence of the extended mass on the gravitational potential becomes notable at distances > ∼ 0.4 pc from Sgr A*. Constraints on the distribution of this extended mass are weak. The extended mass can be explained well by the mass of the stars that make up the cluster.

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“…solution for a parameterized isotropic model using radial velocities of late-type stars . Open rectangles: Non-parametric mass estimator for an isotropic model (Chakrabarty & Saha 2001). "G": Mass estimates from gas Doppler shifts (Genzel & Townes 1987).…”

Section: Statistical Estimatorsmentioning

confidence: 99%