J/AJ/110/1699 F-P observations of globular clusters (Gebhardt+ 1995)
Fabry-Perot observations of globular clusters. II. 47 Tuc, NGC 6397, and M30
Gebhardt K., Pryor C., Williams T.B., Hesser J.E.
<Astron. J. 110, 1699 (1995)>
=1995AJ....110.1699G 1995AJ....110.1699G
ADC_Keywords: Clusters, globular ; Radial velocities
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 5km/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.
Objects:
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RA (2000) DE Designation(s)
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00 23.4 -72 04 47 Tuc = NGC 104
17 40.9 -53 41 NGC 6397
21 40.3 -23 11 M 30 = NGC 7099
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1a 47 802 47 Tuc stars
table1b 43 132 M30 stars
table1c 39 126 NGC 6397 stars
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See also:
1993BAAS...25Q1406P 1993BAAS...25Q1406P : Fabry-Perot observations of globular cluster cores.
J/AJ/113/1026 : Fabry-Perot Observations of M15 (Gebhardt+ 1997)
Byte-by-byte Description of file: table1?
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Bytes Format Units Label Explanations
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1- 5 A5 --- ID Star identification (1)
7- 12 F6.1 arcsec Xpos []? X offset from adopted cluster center (2)
14- 19 F6.1 arcsec Ypos []? Y offset from adopted cluster center (2)
21- 25 F5.1 mag Vmag []? Fabry-Perot V magnitude (3)
27- 32 F6.1 km/s Vel Velocity
34- 37 F4.1 km/s e_Vel Velocity uncertainty (4)
39- 47 A9 --- Note Notes (5)
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Note (1): When a star has many entries, the first line is the weighted mean and
subsequent lines are the individual velocity
Identification prefixes are:
FP Fabry-Perot number
M Mayor et al. (1983A&AS...54..495M 1983A&AS...54..495M)
MDM Meylan et al. (1991ApJ...383..587M 1991ApJ...383..587M)
CA Cordoni & Auriere (1984A&AS...58..559C 1984A&AS...58..559C)
AW Alcaino & Wamsteker (1982A&AS...50..141A 1982A&AS...50..141A)
W Wooley et al. (1961RGOB...43....1W 1961RGOB...43....1W)
V Sawyer-Hogg (1973PDDO....3....6S 1973PDDO....3....6S)
Note (2): Offset in arcseconds from the adopted cluster center, increasing to
the E and N, respectively. These centers are the location of the
peak value of an adaptive kernel estimate (Silverman 1986, Density
Estimation for Statistics and Data Analysis; Chapman and Hall,
London) of the surface density of stars identified in our frames by
DAOPHOT and have uncertainties of approximately 2". For 47 Tuc the
adopted center is within 2" of the center defined by Guhathakurta et
al. 1992AJ....104.1790G 1992AJ....104.1790G. Plausible errors in the adopted centers
have little effect on the dynamical analysis. The relative offsets
for the stellar positions are good to within 0.1".
Note (3): The FP V magnitude should only be used as a rough estimate since a
∼4A bandpass was used and no color terms were included when
transforming the measured counts in continuum into a V magnitude.
Note (4): The uncertainties for the 47 Tuc velocities do not include the
additional 1km/s discussed in section 2 of the printed paper.
Note (5): Additional IDs, the probability of the Chi-square exceeding the
observed value when there are multiple velocity measurements, or the
number "1" if the star is not used in the dynamical analysis due to
restricted velocity coverage at the outer edge of the field.
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Origin: AAS CD-ROM series, Volume 5, 1995 Lee Brotzman [ADS] 31-Oct-1995
(End) [CDS] 25-Jan-1996