CDROM/AJ/V113/P1026     Fabry-Perot Observations of M15 (Gebhardt+ 1997)
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Fabry-Perot Observations of Globular Clusters. III. M15
      Karl Gebhardt, Carlton Pryor, T. B. Williams, James E. Hesser
      and Peter B. Stetson
      <1997, AJ, 113, 1026>
      =1997AJ....113.1026G
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Abstract:
  We have used an Imaging Fabry-Perot Spectrophotometer with the
  Sub-arcsecond Imaging Spectrograph on the Canada-France-Hawaii
  Telescope to measure velocities for 1534 stars in the globular cluster
  M15 (NGC 7078) with uncertainties between 0.5 and 10 km/s.  Combined
  with previous velocity samples, the total number of stars with measured
  velocities in M15 is 1597. An average seeing of 0.8" allowed us to
  obtain velocities for 144 stars within 10" of the center of M15,
  including 12 stars within 2". The velocity dispersion profile for M15
  remains flat at a value of 11 km/s from a radius of 0.4 into our
  innermost reliable point at 0.02 (0.06 pc). Assuming an isotropic
  velocity dispersion tensor, this profile and the previously-published
  surface brightness profile can be equally well represented either by a
  stellar population whose M/L varies with radius from 1.7 in solar units
  at large radii to 3 in the central region, or by a population with a
  constant M/L of 1.7 and a central black hole of 1000 Msun. A
  non-parametric mass model that assumes no black hole, no rotation, and
  isotropy constrains the mass density of M15 to better than 30% at a
  radius of 0.07 parsecs. The mass-density profile of this model is well
  represented by a power law with an exponent of -2.2, the value
  predicted by models of cluster core-collapse. Using the assumption of
  local thermodynamic equilibrium, we estimate the present-day mass
  function and infer a significant number of 0.6-0.7 Msun objects in the
  central few parsecs, 85% of which may be in the form of stellar
  remnants. Not only do we detect rotation; we find that the position
  angle of the projected rotation axis in the central 10" is 100 deg
  different from that of the whole sample. We also detect an increase in
  the amplitude of the rotation at small radii. Although this increase
  needs to be confirmed with better-seeing data, it may be the result of
  a central mass concentration. (Copyright) 1997 American Astronomical
  Society.

File Summary:
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File Name    Lrecl    Records   Explanations
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table1.dat      52       1601   Velocity data
table1.tex      70       1621   AASTeX version of table1.dat
table2.dat      70        512   Repeat measurements
table2.tex     108        537   AASTeX version of table2.dat
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Byte-by-byte Description of file: table1.dat
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   Bytes Format  Units   Label      Explanations
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   1- 5   A5     ---     ID         Star identification
   6-13   F8.1   arcsec  X         *X offset from cluster center (E thru N)
  14-21   F8.1   arcsec  Y         *Y offset from cluster center (E thru N)
  22-29   F8.1   km/s    Vel        Mean velocity
  30-35   F6.1   km/s    e_Vel      Uncertainty in Vel
  36-41   F6.1   mag     V_FP      *Fabry-Perot magnitude
  42-43   2X     ---     ---        Blank
  44-52   A9     ---     Prob      *Probability of the chi-square
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Notes for file: table1.dat
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X, Y:
  The cluster center coordinates are given in Guhathakutra et al.
  1996, AJ, 111, 267.

V_FP:
  Fabry-Perot magnitude, estimated from the fitted continuum of the
  authors' 3 Angstrom spectrum.

Prob:
  The probability of the chi-square from the multiple measurements
  exceeding the observed value -- a low probability suggests a
  variable velocity -- or a note.  A note of 'bias' indicates the
  star is beyond the unbiased radius and is not used in the
  dynamical analysis.  A note of 'non' indicates the star was
  determined to be a non-member based on its radial velocity.
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Byte-by-byte Description of file: table2.dat
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   Bytes Format  Units   Label      Explanations
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   1- 5   A5     ---     ID         Star identification
   6-13   F8.1   km/s    CFHT95     []? Velocity from the 1995 CFHT data
  14-18   F5.1   km/s    e_CFHT95   []? Uncertainty in CFHT95
  19-26   F8.1   km/s    CFHT94     []? Velocity from the 1994 CFHT data
  27-31   F5.1   km/s    e_CFHT94   []? Uncertainty in CFHT94
  32-39   F8.1   km/s    FP92       []? Velocity from 1992 CTIO data (paper I)
  40-44   F5.1   km/s    e_FP92     []? Uncertainty in FP92
  45-52   F8.1   km/s    FP91       []? Velocity from 1991 CTIO data (paper I)
  53-57   F5.1   km/s    e_FP91     []? Uncertainty in FP91
  58-65   F8.1   km/s    PSC        []? Velocity from the PSC
  66-70   F5.1   km/s    e_PSC      []? Uncertainty in PSC
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(End)                                             Lee Brotzman [ADS] 09-Apr-1997