CDROM/APJ/V347/P251 Dynamics of Globular Cluster M15 (Peterson+ 1989) ================================================================================ The Nonthermal Stellar Dynamics of the Globular Cluster M15 Ruth C. Peterson, Patrick Seitzer, and Kyle M. Cudworth <1989, ApJ, 347, 251> =1989ApJ...347..251P ================================================================================ 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 behavior 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 Msun. Keywords: clusters: globular -- radial velocities -- stars: stellar dynamics File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table1.dat 78 120 Velocities for M15 members table2.dat 38 87 Stars with mutiple velocity measurements table3.dat 61 2 Velocities for M15 nonmembers -------------------------------------------------------------------------------- Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 7 F7.2 d Date *Julian date (- 2440000) of each observation 8 1X --- --- Blank 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. 21 1X --- --- Blank 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 V *[]? V magnitude 65-70 I6 --- Kustner *[]? Number from Kustner (1921) 71 1X --- --- Blank 72-78 A7 --- Other *Other star name -------------------------------------------------------------------------------- Notes for file: table1.dat -------------------------------------------------------------------------------- Date: Mean Julian date of each observation, except for stars observed more than once, where the date of the first observation is listed. 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. 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 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. V: V magnitude, from preliminary measurements by Cudworth except for stars inside 0.35', where AC values are used. Kustner: Number from Kustner 1921, Veroff. Sternw. Bonn., No. 15. Other: Other star name: Auriere & Cordoni 1981, A&AS, 46, 347, prefix AC; Sandage 1970, ApJ, 162, 841, prefix S; Arp 1955, AJ, 60, 317, Roman numeral prefix. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 7 F7.2 d Date Julian date (- 2440000) 8- 9 2X --- --- Blank 10-17 F8.2 km/s RV Measured radial velocity 18-23 F6.1 km/s e_RV Internal uncertainty in RV 24 1X --- --- Blank 25-30 I6 --- Kustner *[]? Number from Kustner (1921) 31 1X --- --- Blank 32-38 A7 --- Other *Other star name -------------------------------------------------------------------------------- Notes for file: table2.dat -------------------------------------------------------------------------------- Kustner: Number from Kustner 1921, Veroff. Sternw. Bonn., No. 15. Other: Other star name: Auriere & Cordoni 1981, A&AS, 46, 347, prefix AC; Arp 1955, AJ, 60, 317, Roman numeral prefix. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 7 F7.2 d Date Julian date (- 2440000) of each observation 8- 1X --- --- Blank 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. 21 1X --- --- Blank 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 V V magnitude 54-55 2X --- --- Blank 56-61 I6 --- Kustner *Number from Kustner (1921) -------------------------------------------------------------------------------- Notes for file: table3.dat -------------------------------------------------------------------------------- Kustner: Number from Kustner 1921, Veroff. Sternw. Bonn., No. 15. -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 06-May-1995