J/ApJ/347/251 Dynamics of Globular Cluster M15 (Peterson+ 1989)
The Nonthermal Stellar Dynamics of the Globular Cluster M15
Peterson Ruth C., Seitzer Patrick, Cudworth Kyle M.
<Astrophys. J. 347, 251 (1989)>
=1989ApJ...347..251P 1989ApJ...347..251P
ADC_Keywords: Clusters, globular ; Radial velocities
Keywords: clusters: globular - radial velocities - stars: stellar dynamics
Abstract:
The velocity dispersion as a function of radius in the globular
cluster M15 is derived from measurements of 120 individual stars
between 0.1' and 4.6' of the cluster center, and from the integrated
light of the central cusp. The stellar measurements, with an
individual accuracy of 1 km/s, indicate a mean cluster velocity of
-107.1±0.9 km/s, and a mean velocity dispersion of 9.0±0.6 km/s.
The velocity dispersion inside 1' varies with radius. The dispersion
of the 27 stars within 20" is 14.2±1.9 km/s, while that of the 30
stars between 0.5' and 1.2' is 8.4±1.4 km/s. The cusp itself appears
to have a dispersion of at least 25 km/s. Except for its greater
velocity broadening, the spectrum of the integrated light of the cusp
is indistinguishable from that formed by superposition of the
individual M15 giant spectra, demonstrating that the excess light at
the center is due primarily to the normal M15 population.
The increase of the dispersion toward the center is not consistent
with truncated isothermal (King-Michie) models, for which the velocity
dispersion is nearly constant within a few core radii and then falls
steeply beyond. The observed behaviour is difficult to reconcile as
well with current post-core collapse models, which are also isothermal
and whose central energy sources are modest. It is indicative of a
nonthermal energy distribution with substantial heating in the central
regions; this is consistent with a central black hole of about 1000
M☉.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 78 120 Velocities for M15 members
table2.dat 38 87 Stars with multiple velocity measurements
table3.dat 61 2 Velocities for M15 nonmembers
--------------------------------------------------------------------------------
See also:
J/AJ/106/154 : HST Observations in inner region of M15 (Ferraro+ 1993)
J/AJ/107/1745 : HST UVI photometry of M5. II. (Yanny+, 1994)
J/AJ/107/2067 : Fabry-Perot measurements of M15 (Gebhardt+, 1994)
J/AJ/110/704 : RR Lyrae in M15 (Silbermann+ 1995)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 F7.2 d JD-2440000 *Julian date (-2440000) of each observation
9-11 I3 h RAh *Right ascension (equinox 1950.0)
12-14 I3 min RAm R.A.
15-20 F6.2 s RAs R.A.
22 A1 --- DE- Declination sign (always blank)
23-24 I2 deg DEd Declination (equinox 1950.0)
25-27 I3 arcmin DEm Dec.
28-32 F5.1 arcsec DEs Dec.
33-38 F6.2 arcmin Dist *Radial distance from cluster center
39-44 F6.1 deg PA *Position angle positive north through east
45-53 F9.2 km/s RV *Measured radial velocity
54-57 F4.1 km/s e_RV Internal uncertainty in RV
58-64 F7.2 mag Vmag *[]? V magnitude
65-70 I6 --- Kustner []? Number from Kustner (1921VeUSB..15....1K 1921VeUSB..15....1K)
72-78 A7 --- Other *Other star name
--------------------------------------------------------------------------------
Note on JD-2440000:
Mean Julian date of each observation, except for stars observed more
than once, where the date of the first observation is listed.
Note on RAh:
Equatorial coordinates are as measured by Cudworth, except that AC
[Auriere & Cordoni 1981, A&AS, 46, 347] coordinates were used for
their stars 271, 417, 456, 457, 488, 576, 623, 780, and 787.
Note on Dist, PA:
Radius and position angle from the point marked by the large cross
in Figure 1 of the printed paper, RA = 21h 27m 33.33s,
DE=+11d 56m 48.8s
Note on RV:
For all multiply-observed stars, this is the weighted mean of the
N independent observations in Table 2, except for K912, where the
velocity and uncertainty were derived from the single spectrum
formed by coadding the two separate exposures.
Note on Vmag:
V magnitude, from preliminary measurements by Cudworth except for
stars inside 0.35', where AC values are used.
Note on Other:
Other star name: Auriere & Cordoni (1981A&AS...46..347A 1981A&AS...46..347A) prefix AC;
Sandage (1970ApJ...162..841S 1970ApJ...162..841S) prefix S; Arp (1955AJ.....60..317A 1955AJ.....60..317A)
Roman numeral prefix.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 F7.2 d JD-2440000 Julian date (-2440000)
10-17 F8.2 km/s RV Measured radial velocity
18-23 F6.1 km/s e_RV Internal uncertainty in RV
25-30 I6 --- Kustner []? Number from Kustner (1921VeUSB..15....1K 1921VeUSB..15....1K)
32-38 A7 --- Other *Other star name
--------------------------------------------------------------------------------
Note on Other:
Other star name: Auriere & Cordoni (1981A&AS...46..347A 1981A&AS...46..347A) prefix AC;
Arp (1955AJ.....60..317A 1955AJ.....60..317A) Roman numeral prefix.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 F7.2 d JD-2440000 Julian date (-2440000) of each observation
9-11 I3 h RAh Right ascension (equinox 1950.0)
12-14 I3 min RAm R.A.
15-20 F6.2 s RAs R.A.
22 A1 --- DE- Declination sign (always blank)
23-24 I2 deg DEd Declination (equinox 1950.0)
25-27 I3 arcmin DEm Dec.
28-32 F5.1 arcsec DEs Dec.
33-41 F9.2 km/s RV Measured radial velocity
42-46 F5.1 km/s e_RV Internal uncertainty in RV
47-53 F7.2 mag Vmag V magnitude
56-61 I6 --- Kustner Number from Kustner (1921VeUSB..15....1K 1921VeUSB..15....1K)
--------------------------------------------------------------------------------
References:
Kustner F., 1921, Veroff. Sternw. Bonn, No 15
=1921VeUSB..15....1K 1921VeUSB..15....1K
Origin: AAS CD-ROM series, Volume 4, 1995 Lee Brotzman [ADS] 06-May-1995
(End) [CDS] 11-Jul-1995