THE ASTRONOMICAL JOURNAL    VOLUME 110, NUMBER 4, PAGE 1699        OCTOBER 1995

 FABRY-PEROT OBSERVATIONS OF GLOBULAR CLUSTERS. II. 47 TUC, NGC 6397, AND M30

               KARL GEBHARDT, CARLTON PRYOR, AND T. B. WILLIAMS

      Department of Physics and Astronomy, Rutgers, The State University,
                  Box 0849, Piscataway, New Jersey 08855-0849
   Electronic mail: gebhardt@astro.lsa.umich.edu, pryor@physics.rutgers.edu,
                         williams@physics.rutgers.edu

                                JAMES E. HESSER

    Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics,
          National Research Council of Canada, 5071 W. Saanich Road,
                    R.R. 5, Victoria, B.C., V8X 4M6, Canada
                      Electronic mail: hesser@dao.nrc.ca

                                   ABSTRACT

    Using the Rutgers Imaging Fabry-Perot Spectrophotometer on the CTIO 4-m
    telescope, we have measured radial velocities for 548 stars in 47 Tuc
    (NGC 104), 128 stars in NGC 6397, and 132 stars in M30 (NGC 7099), with
    uncertainties between 0.5 and 5 km/s.  In 47 Tuc and NGC 6397, the
    dispersion profiles at first increase with decreasing radii but then
    flatten in the central 0.4'.  This is the same behavior seen in our
    previously published profile for M15.  The measured stellar velocities
    show that 47 Tuc is rotating, with a projected rotation axis that is
    aligned with the isophotal minor axis.  We also find a similar
    alignment for the rotation that we previously measured in M15.  A map
    of the average velocity in the central regions derived from the
    integrated light shows rotation for NGC 6397 and 47 Tuc.  For 47 Tuc,
    NGC 6397, and M15, the amplitude of the projected rotation measured at
    a radius of 0.6' using the individual stellar velocities is equal to,
    or smaller than, that measured at a radius of 0.2' using the integrated
    light.  This is not consistent with the solid-body rotation usually
    assumed for the inner regions.  To study further the form of the
    projected rotation we have used two-dimensional spline smoothing to
    derive a mean velocity map for 47 Tuc using the individual stellar
    velocities.  This map shows that the projected rotation velocity
    reaches a plateau at a radius of 3' and that the radial dependence of
    the projected rotation velocity deviates significantly from solid body
    beyond 2'.  We have repeat measurements of the two "high-velocity"
    stars of Meylan, Dubath, and Mayor.  However, we detect more stars with
    similar large offsets from the cluster mean velocity.  The number of
    stars that we measure with large velocity offsets is consistent with a
    normal distribution, so that there is no need to invoke a special
    creation mechanism for these stars.