J/ApJ/602/264 Proper motions and radial velocities in M15 (McNamara+, 2004)
The dynamical distance to M15: estimates of the cluster's age and mass and
of the absolute magnitude of its RR Lyrae stars.
McNamara B.J., Harrison T.E., Baumgardt H.
<Astrophys. J., 602, 264-270 (2004)>
=2004ApJ...602..264M 2004ApJ...602..264M
ADC_Keywords: Clusters, globular ; Proper motions ; Radial velocities
Keywords: distance scale - globular clusters: individual (M15)
Abstract:
Newly determined high-precision relative proper motions determined
from the Hubble Space Telescope Wide Field Planetary Camera 2 are used
along with radial velocity measurements to determine the dynamical
distance to the globular cluster M15. A comparison of the proper
motion and radial velocity dispersions from a sample of 237 stars,
located at an average radial distance of about 10" from the cluster
center, yields a cluster distance of 9.98±0.47kpc. This distance
agrees to within the stated errors to other distance estimates but
places this object about 5% closer than the currently adopted value of
10.4kpc. Using this new distance, we estimate that RR Lyrae stars
having [Fe/H]=-2.15 have a value of Mv(RR)=0.51±0.11. We also
estimate that M15 has an age of about 13.2Gyr, which places it among
the oldest of the Galactic globular clusters. From a comparison of the
observed velocity dispersion with results from recent N-body
calculations, we derive a total cluster mass for M15 of
MC=4.5x105M☉.
Description:
The proper motion and radial velocity measurements employed in this
study are those published by McNamara et al. (2003, Cat.
J/ApJ/595/187) and Gebhardt et al. (2000, Cat. J/AJ/119/1268),
respectively. The former investigation relied on Hubble Space
Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) images taken in
1995 and 2003.
Objects:
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RA (2000) DE Designation(s)
-----------------------------------------
21 29 58.4 +12 10 01 M15 = 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 55 242 Proper motion and radial velocity data
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See also:
J/A+AS/119/307 : Position in M15 (Le Campion+, 1996)
J/AJ/106/154 : HST Observations in inner region of M15 (Ferraro+ 1993)
J/AJ/107/1745 : HST UVI photometry of M15. II. (Yanny+, 1994)
J/AJ/110/704 : RR Lyrae Variables in M15 (Silbermann+ 1995)
J/AJ/115/708 : Radial Velocities in the Field of M15 (Drukier+ 1998)
J/AJ/119/1268 : CFHT adaptive optics observations of M15 (Gebhardt+, 2000)
J/AJ/124/3255 : UBV photometry in M15 (van der Marel+, 2002)
J/ApJ/595/187 : Proper motions in M15 (McNamara+, 2003)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 F5.1 pix Xpos X pixel location (1)
7- 11 F5.1 pix Ypos Y pixel location (1)
13- 18 F6.3 10mas/yr pmX Proper motion in X direction
20- 25 F6.3 10mas/yr pmY Proper motion in Y direction
27- 31 F5.3 10mas/yr e_pmX X proper motion error
33- 37 F5.3 10mas/yr e_pmY Y proper motion error
39- 43 I5 --- VGG ID given in Gebhardt et al. (2000,
Cat. J/AJ/119/1268), Cl* NGC 7078 VGG NNNNN
45- 50 F6.1 km/s RV Radial velocity in Gebhardt et al. (2000,
Cat. J/AJ/119/1268)
52- 55 F4.1 km/s e_RV Error in RV
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Note (1): On HST Image WFPC2 U2AS0201T.
The scale of these images is 0.0455"/pix and they cover an area of
36"x36" approximately centered on the cluster core.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 06-Apr-2004