J/ApJ/454/788 Radial velocities and BV photometry of NGC 3201 (Cote+ 1995)
Dynamics of the Galactic globular cluster NGC 3201
Cote P., Welch D.L., Fischer P., Gebhardt K.
<Astrophys. J. 454, 788 (1995)>
=1995ApJ...454..788C 1995ApJ...454..788C (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Radial velocities ; Photometry, CCD
Keywords: globular clusters: individual (NGC 3201) - stars: kinematics -
techniques: radial velocities
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 ∼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/LB∼M/LV∼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.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3 121 930 Radial velocities and photometry
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Byte-by-byte Description of file: table3
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Bytes Format Units Label Explanations
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1- 3 I3 --- Star Star identification number
6- 7 I2 h RAh Right ascension, equinox=J2000.0
9- 10 I2 min RAm Right ascension
11- 16 F6.2 s RAs Right ascension
18 A1 --- DE- Declination sign
19- 20 I2 deg DEd Declination, equinox=J2000.0
22- 23 I2 arcmin DEm Declination
25- 28 F4.1 arcsec DEs Declination
30- 35 F6.2 arcmin Dist Distance from cluster center
38- 49 F12.4 d HJD HJD of radial velocity
52- 57 F6.2 km/s HRV Heliocentric radial velocity
60- 63 F4.2 km/s e_HRV HRV uncertainty
66- 71 F6.2 km/s HRVmean Weighted mean heliocentric radial velocity
74- 77 F4.2 km/s e_HRVmean HRVmean uncertainty
80- 84 F5.2 mag Vmag Apparent V magnitude
87- 90 F4.2 mag B-V Apparent B-V color
93- 94 I2 --- o_HRV Number of radial velocity measurements
96-101 F6.2 --- Chi2 Chi-square for radial velocities
103-108 F6.2 --- Chi2_R []? Reduced chi-square for radial velocities
111-116 F6.4 --- Prob [0/1]? Probability of obtaining a chi-square
this large purely as a consequence of
measurement error
119-121 A3 --- Src Source of photometry, 'APM' or 'CCD'
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Origin: AAS CD-ROM series, Volume 5, 1995 Lee Brotzman [ADS] 05-Nov-95
(End) Patricia Bauer [CDS] 24-Oct-1996