We describe a correlation between the mass of a galaxy's central black hole and the luminosity-weighted M bh line-of-sight velocity dispersion within the half-light radius. The result is based on a sample of 26 galaxies, j e including 13 galaxies with new determinations of black hole masses from errors. The -relation is of interest not only for its strong predictive power but also because it implies that M j bh e central black hole mass is constrained by and closely related to properties of the host galaxy's bulge.

We derive improved versions of the relations between supermassive black hole mass (M BH ) and host-galaxy bulge velocity dispersion (σ) and luminosity (L) (the M-σ and M-L relations), based on 49 M BH measurements and 19 upper limits. Particular attention is paid to recovery of the intrinsic scatter (ε 0 ) in both relations. We find log(M BH /M ) = α + β log(σ/200 km s −1 ) with (α, β, ε 0 ) = (8.12 ± 0.08, 4.24 ± 0.41, 0.44 ± 0.06) for all galaxies and (α, β, ε 0 ) = (8.23 ± 0.08, 3.96 ± 0.42, 0.31 ± 0.06) for ellipticals. The results for ellipticals are consistent with previous studies, but the intrinsic scatter recovered for spirals is significantly larger. The scatter inferred reinforces the need for its consideration when calculating local black hole mass function based on the M-σ relation, and further implies that there may be substantial selection bias in studies of the evolution of the M-σ relation. We estimate the M-L relationship as log(M BH /M ) = α + β log(L V /10 11 L ,V ) of (α, β, ε 0 ) = (8.95 ± 0.11, 1.11 ± 0.18, 0.38 ± 0.09); using only early-type galaxies. These results appear to be insensitive to a wide range of assumptions about the measurement errors and the distribution of intrinsic scatter. We show that culling the sample according to the resolution of the black hole's sphere of influence biases the relations to larger mean masses, larger slopes, and incorrect intrinsic residuals.

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Black hole masses predicted from the M • − σ relationship conflict with those predicted from the M • − L relationship for the most luminous galaxies, such as brightest cluster galaxies (BCGs). This is because stellar velocity dispersion, σ, increases only weakly with luminosity for BCGs and other giant ellipticals. The M • − L relationship predicts that the most luminous BCGs may harbor black holes with M • approaching 10 10 M ⊙ , while the M • − σ relationship always predicts M • < 3 × 10 9 M ⊙ . Lacking direct determination of M • in a sample of the most luminous galaxies, we advance arguments that the M • − L relationship is a plausible or even preferred description for BCGs and other galaxies of similar luminosity. Under the hypothesis that cores in central stellar density are formed by binary black holes, the inner-core cusp radius, r γ , may be an independent witness of M • . Using central structural parameters derived from a large sample of early-type galaxies observed by HST, we argue that L is superior to σ as an indicator of r γ in luminous galaxies. Further, the observed r γ − M • relationship for 11 core galaxies with measured M • appears to be consistent with the M • − L relationship for BCGs. BCGs have large cores appropriate for their large luminosities that may be difficult to generate with the more modest black hole masses inferred from the M • − σ relationship. M • ∼ L may be expected to hold for BCGs, if they were formed in dissipationless mergers, which should preserve ratio of black hole to stellar mass. This picture appears to be consistent with the slow increase in σ with L and the more rapid increase in effective radii, R e , with L seen in BCGs as compared to less luminous galaxies. If BCGs have large BHs commensurate with their high luminosities, then the local black hole mass function for M • > 3 × 10 9 M ⊙ may be nearly an order of magnitude richer than what would be inferred from the M • − σ relationship. The volume density of the most luminous QSOs at earlier epochs may favor the predictions from the M • − L relationship.

We present observations of 77 early-type galaxies imaged with the PC1 CCD of the Hubble Space Telescope (HST ) WFPC2. ''Nuker-law'' parametric fits to the surface brightness profiles are used to classify the central structure into ''core'' or ''power-law'' forms. Core galaxies are typically rounder than power-law galaxies. Nearly all power-law galaxies with central ellipticities ! 0:3 have stellar disks, implying that disks are present in powerlaw galaxies with < 0:3 but are not visible because of unfavorable geometry. A few low-luminosity flattened core galaxies also have disks; these may be transition forms from power-law galaxies to more luminous core galaxies, which lack disks. Several core galaxies have strong isophote twists interior to their break radii, although power-law galaxies have interior twists of similar physical significance when the photometric perturbations implied by the twists are evaluated. Central color gradients are typically consistent with the envelope gradients; core galaxies have somewhat weaker color gradients than power-law galaxies. Nuclei are found in 29% of the core galaxies and 60% of the power-law galaxies. Nuclei are typically bluer than the surrounding galaxy. While some nuclei are associated with active galactic nuclei (AGNs), just as many are not; conversely, not all galaxies known to have a low-level AGN exhibit detectable nuclei in the broadband filters. NGC 4073 and 4382 are found to have central minima in their intrinsic starlight distributions; NGC 4382 resembles the double nucleus of M31. In general, the peak brightness location is coincident with the photocenter of the core to a typical physical scale of <1 pc. Five galaxies, however, have centers significantly displaced from their surrounding cores; these may be unresolved asymmetric double nuclei. Finally, as noted by previous authors, central dust is visible in about half of the galaxies. The presence and strength of dust correlates with nuclear emission; thus, dust may outline gas that is falling into the central black hole. The prevalence of dust and its morphology suggest that dust clouds form, settle to the center, and disappear repeatedly on $10 8 yr timescales. We discuss the hypothesis that cores are created by the decay of a massive black hole binary formed in a merger. Apart from their brightness profiles, there are no strong differences between core galaxies and power-law galaxies that demand this scenario; however, the rounder shapes of core, their lack of disks, and their reduced color gradients may be consistent with it.

We present Hubble Space Telescope (HST ) spectroscopy of the nucleus of M31 obtained with the Space Telescope Imaging Spectrograph (STIS). Spectra that include the Ca ii infrared triplet (k ' 8500 8) see only the red giant stars in the double brightness peaks P1 and P2. In contrast, spectra taken at k ' 3600 5100 8 are sensitive to the tiny blue nucleus embedded in P2, the lower surface brightness nucleus of the galaxy. P2 has a K-type spectrum, but we find that the blue nucleus has an A-type spectrum: it shows strong Balmer absorption lines. Hence, the blue nucleus is blue not because of AGN light but rather because it is dominated by hot stars. We show that the spectrum is well described by A0 giant stars, A0 dwarf stars, or a 200 Myr old, single-burst stellar population. White dwarfs, in contrast, cannot fit the blue nucleus spectrum. Given the small likelihood for stellar collisions, recent star formation appears to be the most plausible origin of the blue nucleus. In stellar population, size, and velocity dispersion, the blue nucleus is so different from P1 and P2 that we call it P3 and refer to the nucleus of M31 as triple.Because P2 and P3 have very different spectra, we can make a clean decomposition of the red and blue stars and hence measure the light distribution and kinematics of each uncontaminated by the other. The line-of-sight velocity distributions of the red stars near P2 strengthen the support for Tremaine's eccentric disk model. Their wings indicate the presence of stars with velocities of up to 1000 km s À1 on the anti-P1 side of P2.The kinematics of P3 are consistent with a circular stellar disk in Keplerian rotation around a supermassive black hole. If the P3 disk is perfectly thin, then the inclination angle i ' 55 is identical within the errors to the inclination of the eccentric disk models for P1+P2 by Peiris & Tremaine and by Salow & Statler. Both disks rotate in the same sense and are almost coplanar. The observed velocity dispersion of P3 is largely caused by blurred rotation and has a maximum value of ¼ 1183 AE 201 km s À1 . This is much larger than the dispersion ' 250 km s À1 of the red stars along the same line of sight and is the largest integrated velocity dispersion observed in any galaxy. The rotation curve of P3 is symmetric around its center. It reaches an observed velocity of V ¼ 618 AE 81 km s À1 at radius 0B05 ¼ 0:19 pc, where the observed velocity dispersion is ¼ 674 AE 95 km s À1 . The corresponding circular rotation velocity at this radius is $1700 km s À1 . We therefore confirm earlier suggestions that the central dark object interpreted as a supermassive black hole is located in P3.Thin-disk and Schwarzschild models with intrinsic axial ratios b/a P 0:26 corresponding to inclinations between 55 and 58 match the P3 observations very well. Among these models, the best fit and the lowest black hole mass are obtained for a thin-disk model with M ¼ 1:4 ; 10 8 M . Allowing P3 to have some intrinsic thickness and considering possible systematic errors, the 1 confi...

This is the first of a series of papers dedicated to unveiling the mass composition and dynamical structure of a sample of flattened early‐type galaxies in the Coma cluster. We describe our modifications to the Schwarzschild code of Richstone et al. Applying a Voronoi tessellation in the surface of section, we are able to assign accurate phase‐space volumes to individual orbits and to reconstruct the full three‐integral phase‐space distribution function (DF) of any axisymmetric orbit library. Two types of tests have been performed to check the accuracy with which DFs can be represented by appropriate orbit libraries. First, by mapping DFs of spherical γ‐models and flattened Plummer models onto the library, we show that the resulting line‐of‐sight velocity distributions and internal velocity moments of the library match those derived directly from the DF to a precision better than that of present‐day observational errors. Secondly, by fitting libraries to the projected kinematics of the same DFs, we show that the DF reconstructed from the fitted library matches the input DF to a rms of about 15 per cent over a region in phase space covering 90 per cent of the mass of the library. The accuracy achieved allows us to implement effective entropy‐based regularization to fit real, noisy and spatially incomplete data.

The stellar kinematics of the dwarf elliptical galaxy NGC 4486B have been measured in seeing sigma_* = .22 arcsec with the Canada-France-Hawaii Telescope. Lauer et al. 1996, ApJ, 471, L79 have shown that NGC 4486B is similar to M31 in having a double nucleus. We show that it also resembles M31 in its kinematics. The velocity dispersion gradient is very steep: sigma increases from 116 +- 6 km/s at r = 2" - 6" to 281 +- 11 km/s at the center. This is much higher than expected for an elliptical galaxy of absolute magnitude M_B = -16.8: NGC 4486B is far above the scatter in the Faber-Jackson correlation between sigma and bulge luminosity. Therefore the King core mass-to-light ratio, M/L_V = 20, is unusually high compared with normal values for old stellar populations. We construct dynamical models with isotropic velocity dispersions and show that they reproduce black hole (BH) masses derived by more detailed methods. We also fit axisymmetric, three-integral models. Isotropic models imply that NGC 4486B contains a central dark object, probably a BH, of mass M_BH = 6^{+3}_{-2} x 10^8 M_sun. However, anisotropic models fit the data without a BH if the ratio of radial to azimuthal dispersions is ~ 2 at 1". Therefore this is a less strong BH detection than the ones in M31, M32, and NGC 3115. A 6 x 10^8 M_sun BH is 9 % of the mass M_bulge in stars; even if M_BH is smaller than the isotropic value, M_BH/M_bulge is likely to be unusually large. Double nuclei are a puzzle because the dynamical friction timescales for self-gravitating star clusters in orbit around each other are short. Since both M31 and NGC 4486B contain central dark objects, our results support models in which the survival of double nuclei is connected with the presence of a BH (e. g., Tremaine 1995, AJ, 110, 628).Comment: 5 pages, 5 figs, TeX, ApJL in pres