J/ApJ/420/612 Proper motions & radial velocities in M22 (Peterson+ 1994)
Proper motions and radial velocities in the globular cluster M22 and the cluster distance Peterson R.C., Cudworth K.M. <Astrophys. J. 420, 612 (1994)> =1994ApJ...420..612P
ADC_Keywords: Clusters, globular ; Radial velocities ; Stars, distances Keywords: astrometry - globular clusters: individual (M22) - stars: distances - techniques: radial velocities Abstract: The distance to the globular cluster M22 is reexamined from new radial-velocity data and revised proper motions. Proper motions are rederived for 672 stars in the field of M22 using plate constant solutions from which stars of large proper motions have been removed, to reduce systematic errors which depend on coordinates. Radial velocities good to 1km/s have been obtained for 130 members of the globular cluster M22. The mean radial velocity is -148.8±0.8km/s. The radial velocity dispersion is 6.6±0.8km/s in the mean, and shows little if any dependence on distance from the cluster center over a 3'-7' annulus. Ignoring the small effect of rotation, a mass-to-light ratio M/L_V=0.85±0.15 in solar units is derived. The lack of stars moving faster than the escape velocity suggests strongly that a value M/L_V∼1 applies to the cluster as a whole. This value is among the lowest observed for any globular cluster. Rotation is evident in both proper motions and radial velocities, and its position angle is in reasonable agreement with the major axis of the cluster's elongation. Its amplitude diminishes with radius, from ∼6km/s for 1'≤r≤ 3', to ∼3km/s for 3'≤r≤7'. Rotation must be carefully modeled to determine an accurate distance to the cluster. From the simple approximation that the velocity dispersion is unaffected in the directions perpendicular to the streaming motion, a comparison of the dispersions in proper motion with those in radial velocity leads to a preliminary estimate for the distance of 2.6±0.3kpc, and a horizontal-branch magnitude M_V=0.71±0.27, using the reddening value E(B-V)=0.42 from M22 BHB stars. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 86 130 Velocities for M22 members table3.dat 86 1 *Velocities for M22 field stars table4.dat 37 57 Stars with multiple velocity measurements
Note on table3.dat: This table lists the same information as in Table 2 for the nonmember star. The velocity of this star differs by nearly 100 km/s from that of the cluster.
Byte-by-byte Description of file: table2.dat table3.dat
Bytes Format Units Label Explanations
1- 7 F7.2 d HJD-2440000 *Julian date (-2440000) of each observation 10- 11 I2 h RAh Right ascension (equinox 1950.0) 13- 14 I2 min RAm Right ascension (equinox 1950.0) 16- 20 F5.2 s RAs Right ascension (equinox 1950.0) 22 A1 --- DE- Declination sign 23- 24 I2 deg DEd Declination (equinox 1950.0) 26- 27 I2 arcmin DEm Declination (equinox 1950.0) 29- 32 F4.1 arcsec DEs Declination (equinox 1950.0) 34- 37 F4.1 arcmin Dist *Radial distance from cluster center 39- 44 F6.1 deg PA *Position angle positive north through east 46- 53 F8.2 km/s RV *Measured radial velocity 55- 58 F4.2 km/s e_RV *Internal one-sigma uncertainty in RV 60- 65 F6.2 mag Vmag V magnitude 67- 69 I3 % Memb Percent probability of membership 72- 86 A15 --- ID *Identification
Note on HJD-2440000: Julian date of each observation, or that of the first observation if the star was observed twice or more. Note on Dist, PA: Radius and position angle from the center of the cluster, RA = 18h 33m 21.5s, DE = -23d 56m 44s, as measured by Shawl & White (1986AJ.....91..312S) Note on RV: For all multiply observed stars, this is the weighted mean of the set of observations in Table 4. Note on e_RV: The uncertainty is derived from the ratio R of the height of the cross-correlation peak relative to a typical noise fluctuation, according to the Tonry & Davis (1979AJ.....84.1511T) formula sigma_R=K/(1+R) (in km/s), with K=8.3 for sharp-lined spectra obtained with the Mount Hopkins echelle spectrographs. Note on ID: First, when available, is the identification of Arp & Melbourne (1959AJ.....64...28A) or its extension by Lloyd-Evans (1975MNRAS.171..647L), with Roman numerals I-IV for the quadrants and V for the center. This is followed by identification from Alcaino (1977A&AS...29..383A) and the extension by Alcaino & Liller (1983AJ.....88.1330A), for which the annulus number precedes the number of the star. Last comes the variable number from Sawyer-Hogg (1973PDDO....3....6S), prefix V, no hyphen. If no other name is available, table2 list the Cudworth (1986AJ.....92..348C) number, preceded by C.
Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
1- 8 F8.3 d HJD-2440000 Julian date (-2440000) of each observation 10- 17 F8.2 km/s RV Measured radial velocity 19- 22 F4.2 km/s e_RV Internal uncertainty in RV 24- 29 F6.2 mag Vmag ? V magnitude 32- 37 A6 --- ID *Identification
Note on ID: Arp & Melbourne (1959AJ.....64...28A) or its extension by Lloyd-Evans (1975MNRAS.171..647L), with Roman numerals I-IV for the quadrants. Sawyer-Hogg (1973PDDO....3....6S), prefix V, no hyphen.
Origin: AAS CD-ROM series, Volume 4, 1995 Lee Brotzman [ADS] 06-May-1995
(End) [CDS] 11-Jul-1995
|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|