We have used the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST) to obtain high spatial resolution spectroscopy of the central region of the dense globular cluster M15. The observational strategy and data reduction were described in Paper I (van der Marel et al. 2002). Here we analyze the extracted spectra with a cross-correlation technique to determine the line-of-sight velocities of individual stars. Our final STIS velocity sample contains 64 stars, two-thirds of which have their velocity measured for the first time. The new data set triples the number of stars with measured velocities in the central projected R ≤ 1 ′′ of M15 and doubles the number in the central R ≤ 2 ′′ . We combine our data with existing ground-based data to obtain non-parametric estimates of the radial profiles of the projected rotation velocity, velocity dispersion, and RMS velocity σ RMS . The results differ from earlier work in the central few arcsec in that we find that σ RMS rises to ∼ 14 km s −1 , somewhat higher than the values of 10-12 km s −1 inferred previously from ground-based data.To interpret the results we construct dynamical models based on the Jeans equation for a spherical system. If the velocity distribution is isotropic, then M15 must have a central concentration of non-luminous material. If this is due to a single black hole, then a fit to the full velocity information as function of radius implies that its mass is M BH = (3.9 ± 2.2) × 10 3 M ⊙ . The existence of intermediate-mass black holes in globular clusters is consistent with several scenarios for globular cluster evolution proposed in the literature. The inferred mass for M15 is consistent with the extrapolation of the relation between M BH and σ RMS that has been established for galaxies. Therefore, these results may have important implications for our understanding of the evolution of globular clusters, the growth of black holes, the connection between globular cluster and galaxy formation, and the nature of the recently discovered 'ultra-luminous' X-ray sources in nearby galaxies. Instead of a single intermediate-mass black hole, M15 could have a central concentration of dark remnants (e.g., neutron stars) due to mass segregation. However, we argue that the best-fitting Fokker-Planck models that have previously been constructed for M15 do not predict a central mass concentration that is sufficient to explain the observed kinematics. To fit the M15 data without any central dark mass concentration one must assume that the velocity distribution is significantly radially anisotropic near the center, which contradicts predictions from both Fokker-Planck and N -body calculations.

We report new chemical abundances of 23 bright red giant members of the globular cluster M3, based on high-resolution (R ∼ 45000) spectra obtained with the Keck I telescope. The observations, which involve the use of multislits in the HIRES Keck I spectrograph, are described in detail.Combining these data with a previously-reported small sample of M3 giants obtained with the Lick 3m telescope, we compare metallicities and [X/Fe] ratios for 28 M3 giants with a 35-star sample in the similar-metallicity cluster M13, and with Galactic halo field stars having [Fe/H] < -1. For elements having atomic number A ≥ A(Si), we derive little difference in [X/Fe] ratios in the M3, M13 or halo field samples.All three groups exhibit C depletion with advancing evolutionary state beginning at the level of the red giant branch "bump", but the overall depletion of about 0.7 to 0.9 dex seen in the clusters is larger than that associated with the field stars. The behaviors of O, Na, Mg and Al are distinctively different among the three stellar samples. Field halo giants and subdwarfs have a positive correlation of Na with Mg, as predicted from explosive or hydrostatic carbon burning in Type II supernova sites. Both M3 and M13 show evidence of high-temperature proton capture synthesis from the ON, NeNa, and MgAl cycles, while there is no evidence for such synthesis among halo field stars. But the degree of such extreme proton-capture synthesis in M3 is smaller than it is in M13: the M3 giants exhibit only modest deficiencies of O and corresponding enhancements of Na, less extreme overabundances of Al, fewer stars with low Mg and correspondingly high Na, and no indication that O depletions are a function of advancing evolutionary state as has been claimed for M13.We have also considered NGC 6752, for which Mg isotopic abundances have been reported by Yong et al. (2003). Giants in NGC 6752 and M13 satisfy the same anticorrelation of O abundances with the ratio ( 25 Mg+ 26 Mg)/ 24 Mg, which measures the relative contribution of rare to abundant isotopes of Mg. This points to a scenario in which these

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