J/AJ/113/1026 Fabry-Perot Observations of M15 (Gebhardt+ 1997)
Fabry-Perot Observations of Globular Clusters. III. M15
Gebhardt K., Pryor C., Williams T.B., Hesser J.E., Stetson P.B.
<Astron. J. 113, 1026 (1997)>
=1997AJ....113.1026G 1997AJ....113.1026G
ADC_Keywords: Clusters, globular ; Radial velocities
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 10km/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 11km/s from a radius of 0.4 into our
innermost reliable point at 0.02 (0.06pc). 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 1000M☉. 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 M☉ 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 100deg
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.
Objects:
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RA (2000) DE Designation(s)
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21 29 58.3 +12 10 00 M 15 = NGC 7078
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 53 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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See also:
J/AJ/110/1699 : Paper II. (47 Tuc, NGC 6397 & M30) (Gebhardt+ 1995)
J/ApJ/347/251 : Dynamics of Globular Cluster M15 (Peterson+ 1989)
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
7- 13 F7.1 arcsec Xpos *X offset from cluster center (eastward)
15- 21 F7.1 arcsec Ypos *Y offset from cluster center (northward)
23- 29 F7.1 km/s Vel Mean velocity
31- 35 F5.1 km/s e_Vel Uncertainty in Vel
37- 41 F5.1 mag V(FP) *Fabry-Perot magnitude
44- 48 F5.3 % Prob *? Probability of the chi-square
50- 53 A4 --- Note *Note
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Note on Xpos, Ypos:
The cluster center coordinates are given in Guhathakutra et al.
1996AJ....111..267G 1996AJ....111..267G
Note on V(FP):
Fabry-Perot magnitude, estimated from the fitted continuum of the
authors' 3 Angstrom spectrum.
Note on 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.
Note on 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
7- 13 F7.1 km/s CFHT95 ? Velocity from the 1995 CFHT data
15- 18 F4.1 km/s e_CFHT95 ? Uncertainty in CFHT95
20- 26 F7.1 km/s CFHT94 ? Velocity from the 1994 CFHT data
28- 31 F4.1 km/s e_CFHT94 ? Uncertainty in CFHT94
33- 39 F7.1 km/s FP92 ? Velocity from 1992 CTIO data (paper I,
Pryor et al., 1993BAAS...25Q1406P 1993BAAS...25Q1406P)
41- 44 F4.1 km/s e_FP92 ? Uncertainty in FP92
46- 52 F7.1 km/s FP91 ? Velocity from 1991 CTIO data (paper I,
Pryor et al., 1993BAAS...25Q1406P 1993BAAS...25Q1406P)
54- 57 F4.1 km/s e_FP91 ? Uncertainty in FP91
59- 65 F7.1 km/s PSC ? Velocity from Peterson et al. (1989)
(Cat. J/ApJ/347/251)
67- 70 F4.1 km/s e_PSC ? Uncertainty in PSC
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Origin: AAS CD-ROM series, Volume 8, 1997 Lee Brotzman [ADS] 09-Apr-1997
References:
Pryor et al., Paper I. 1993BAAS...25Q1406P 1993BAAS...25Q1406P
(End) [CDS] 04-Jul-1997