J/ApJ/454/788 J/ApJ/454/788 Radial velocities and BV photometry of NGC 3201 P Cote D L Welch P Fischer K Gebhardt Astrophys. J. 454 788 1995 1995ApJ...454..788C Clusters, globular Photometry, CCD Radial velocities globular clusters: individual (NGC 3201) stars: kinematics techniques: radial velocities BV CCD frames have been used to derive surface brightness profiles for NGC 3201 which extend out to ~18'. A total of 857 radial velocities with median precision ~1km/s for 399 member giants have been used to trace the velocity dispersion profile out to 32.1' (the approximate tidal radius determined from fits of single-mass, isotropic King-Michie models to the cluster surface brightness profiles). The median difference in radial velocity for stars on either side of an imaginary axis stepped through the cluster in 1 deg increments shows a statistically significant maximum amplitude of 1.22+/-0.25km/s. We discuss several possible explanations of this result, including (1) cluster rotation, (2) preferential stripping of stars on prograde orbits near the limiting radius, (3) the projection of the cluster space velocity onto the plane of the sky, and (4) a slight drift in the velocity zero point. It is difficult to unambiguously identify the primary cause of the observed structure in the velocity field, however, and we suspect that all of the above processes may play a role. The BV surface brightness profiles and radial velocities have been modeled with both single- and multimass King-Michie models and nonparametric techniques. The corresponding density profiles and M/L profiles show good agreement over the interval 1.5<~R<~10pc, and both approaches suggest a steady rise in M/L with distance from the cluster center. Due to the low cluster luminosity we are unable to place useful constraints on the anisotropy of M/L_B~M/L_V~2.0+/-0.2 for the multimass and nonparametric models, compared to ~1.65+/-0.15 for models having equal-mass stars. Our best-fit, multimass models have mass function slopes of x~0.75+/-0.25, consistent with recent findings that the form of the mass function depends on the position relative to the potential of the Galaxy.

Star Star identification number --- RAh Right ascension, equinox=2000.0 h RAm Right ascension min RAs Right ascension s DE- Declination sign --- DEd Declination, equinox=2000.0 deg DEm Declination arcmin DEs Declination arcsec Dist Distance from cluster center arcmin HJD HJD of radial velocity d HRV Heliocentric radial velocity km/s e_HRV HRV uncertainty km/s HRVmean Weighted mean heliocentric radial velocity km/s e_HRVmean HRVmean uncertainty km/s Vmag Apparent V magnitude mag B-V Apparent B-V color mag o_HRV Number of radial velocity measurements --- Chi2 Chi-square for radial velocities --- Chi2_R Reduced chi-square for radial velocities --- Prob Probability of obtaining a chi-square this large purely as a consequence of measurement error --- Src Source of photometry, 'APM' or 'CCD' --- Patricia Bauer CDS 1996Oct24AAS CD-ROM series, Volume 5, 1995 Lee Brotzman [ADS] 05-Nov-95 J_ApJ_454_788.xml