CDROM/APJ/V454/P788 Dynamics of the Galactic Glob. Cl. NGC 3201(Cote+ 1995) ================================================================================ Dynamics of the Galactic Globular Cluster NGC 3201 Patrick Cote, Douglas L. Welch, Philippe Fischer, & K. Gebhardt <1995, ApJ, 454, 788> =1995ApJ...455..788C ================================================================================ Abstract: 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 ~ 1 km/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 +/- 0.25 km/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 <~ 10 pc, 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. Keywords: globular clusters: individual (NGC 3201) -- stars: kinematics -- techniques: radial velocities File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table3.dat 118 930 Radial velocities and photometry -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 3 I3 --- Star []? Star identification number 4 1X --- --- Blank 5- 7 I3 h RAh Right ascension, epoch 2000.0 8-10 I3 min RAm R.A. 11-16 F6.2 s RAs R.A. 17 1X --- --- Blank 18 A1 --- DE- Declination sign 19-20 I2 deg DEd Declination, epoch 2000.0 21-23 I3 arcmin DEm Dec. 24-28 F5.1 arcsec DEs Dec. 29-35 F7.2 arcmin Dist Distance from cluster center 36-46 D11.5 --- HJD HJD of radial velocity (-2440000.0) 47-54 F8.2 km/s RV Heliocentric radial velocity 55-60 F6.2 km/s e_RV RV uncertainty 61-68 F8.2 km/s RV_M Weighted mean heliocentric radial velocity 69-74 F6.2 km/s e_RV_M RV_M uncertainty 75-81 F7.2 mag V Apparent V magnitude 82-87 F6.2 mag B-V Apparent B-V color 88-91 I4 --- NRV Number of radial velocity measurements 92-98 F7.2 --- Chi2 Chi-square for radial velocities 99-105 F7.2 --- Chi2_R []? Reduced chi-square for radial velocities 106-113 F8.4 --- Prob []? Probability of obtaining a chi-square this large purely as a consequence of measurement error 114-115 2X --- --- Blank 116-118 A3 --- Src Source of photometry, 'APM' or 'CCD' -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 05-Nov-95