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J/ApJ/595/187       Proper motions in M15                    (McNamara+, 2003)

Does M15 possess an intermediate-mass black hole in its core? McNamara B.J., Harrison T.E., Anderson J. <Astrophys. J. 595, 187 (2003)> =2003ApJ...595..187M
ADC_Keywords: Clusters, globular ; Proper motions ; Photometry, UBV Keywords: astrometry - black hole physics - globular clusters: individual: M15 - methods: N-body simulations - stellar dynamics Abstract: We present the results of an internal proper motion analysis of the inner region of M15 using Hubble Space Telescope Wide Field Planetary Camera 2 images. The motions of 704 stars with brightnesses above that of the cluster turnoff (V<18.3) are analyzed to determine the velocity dispersion profile within about 15" of the cluster center. The average signal-to-noise ratio of these motions is about 3, and stars in the innermost radial bin have an average core distance of only 0.7". Assuming a distance to M15 of 10kpc, we estimate that the velocity dispersion within this innermost bin is 14.5±2.5km/s and that it slowly decreases outward, reaching a value of 9.8±0.8km/s at R=15.6". We find that the proper-motion dispersion profile is in good agreement with the predictions of recent N-body simulations that do not require the presence of a central intermediate-mass black hole (IMBH). The agreement between the observed profile and the N-body simulations is marginally improved if one assumes that when a neutron star is created as a result of stellar evolution, it escapes from the cluster. Based on the results of this study and a review of other investigations, it is concluded that there is little direct evidence that M15 possesses an intermediate-mass black hole. Description: M15 HST WFPC2 images were employed. These images consist of four first-epoch exposures obtained on 1994 April 7 and 12 additional exposures obtained on 2002 April 5 as part of our HST project GO-09039. Both sets of images were acquired with the WFPC2 filter F555W. Longer exposure times were used for the 2002 April images to increase the accuracy of the measured stellar positions. Objects: ---------------------------------------------------------- RA (2000) DE Designation(s) ---------------------------------------------------------- 21 29 58.4 +12 10 01 M15 = NGC 7078 ---------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 57 1764 M15 Proper Motion Data
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/113/1026 : Fabry-Perot Observations of M15 (Gebhardt+ 1997) 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/ApJ/602/264 : Proper motions and radial velocities in M15 (Mcnamara+, 2004) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 5 F5.1 pix Xpix The x position on HST image U2AS0201T (1) 7- 11 F5.1 pix Ypix The y position on HST image U2AS0201T (1) 13- 18 F6.3 0.125pix/yr Xpm The X pixel displacement relative proper motion over 8 years (in pix/8yr) 20- 25 F6.3 0.125pix/yr Ypm The Y pixel displacement relative proper motion over 8 years (in pix/8yr) 27- 31 F5.3 0.125pix/yr e_Xpm Error in Xpm 33- 37 F5.3 0.125pix/yr e_Ypm Error in Ypm 39- 44 F6.2 mag Vmag Uncalibrated instrumental V magnitude 46- 49 F4.2 mag B-V Uncalibrated instrumental (B-V) magnitude 51- 55 I5 --- GID Guhathakurta et al. (1996AJ....111..267G) identification number 57 I1 --- IM [0/1] Internal proper motion analysis (2)
Note (1): The (x,y)-positions are in units of pixels and correspond to the position on HST image U2AS0201T, This image is accessible from the HST archive (http://archive.stsci.edu/hst/index.html). In Simbad, objects are identified as [MHA2003] XXX.x-YYY.y Note (2): Internal proper motion analysis: 1 = used to compute internal motion dispersions; 0 = not used for this purpose.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 17-Nov-2003
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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