C. Lopez

THE SOUTHERN PROPER MOTION PROGRAM. IV. THE SPM4 CATALOG

We present the fourth installment of the Yale/San Juan Southern Proper Motion Catalog, SPM4. The SPM4 contains absolute proper motions, celestial coordinates, and B, V photometry for over 103 million stars and galaxies between the south celestial pole and -20{sup 0} declination. The catalog is roughly complete to V = 17.5 and is based on photographic and CCD observations taken with the Yale Southern Observatorys double astrograph at Cesco Observatory in El Leoncito, Argentina. The proper-motion precision, for well-measured stars, is estimated to be 2-3 mas yr{sup -1}, depending on the type of second-epoch material. At the bright end, proper motions are on the International Celestial Reference System by way of Hipparcos Catalog stars, while the faint end is anchored to the inertial system using external galaxies. Systematic uncertainties in the absolute proper motions are on the order of 1 mas yr{sup -1}.

Relative proper motions and the stellar velocity dispersion of the open cluster M67

Relative proper motions for 663 stars in the field of the old open cluster M67 have been determined using 44 Yerkes 40-in refractor plates. The resulting proper-motion marginal distributions have been fit with a two-component model representing the sum of a cluster distribution and a much wider field distribution, both of which are assumed to be intrinsically Gaussian in form. The observed marginal distributions are actually quite non-Gaussian due to the effects of the proper-motion measurement errors, and thus a modeling procedure that realistically includes the measurement errors has been devised. The procedure yields excellent fits to the observed distributions, and thus allows reliable cluster-membership probabilities to be calculated. The clusters intrinsic velocity dispersion is estimated from the proper motions of the about 80 brightest cluster stars to be 0.81 + or - 0.10 km/s. This is marginally higher than a dispersion estimate based on published radial-velocity measurements of a similar sample of cluster members. 16 refs.

SPACE VELOCITIES OF SOUTHERN GLOBULAR CLUSTERS. V. A LOW GALACTIC LATITUDE SAMPLE

We have measured the absolute proper motions of globular clusters NGC 2808, 3201, 4372, 4833, 5927, and 5986. The proper motions are on the Hipparcos system, and they are the first determinations ever made for these low Galactic latitude clusters. The proper-motion uncertainties range from 0.3 to 0.5 mas yr-1. The inferred orbits indicate that (1) the single metal-rich cluster in our sample, NGC 5927, dynamically belongs to the thick disk; (2) the remaining metal-poor clusters have rather low-energy orbits of high eccentricity, and among these there appear to be two pairs of dynamically associated clusters; (3) the most energetic cluster in our sample, NGC 3201, is on a highly retrograde orbit?which had already been surmised from radial velocity alone?with an apocentric distance of 22 kpc; and (4) none of the metal-poor clusters appear to be associated with the recently detected SDSS streams or with the Monoceros structure. These are the first results of the Southern Proper Motion program where the second-epoch observations are taken with the recent CCD camera system installed on the double astrograph at El Leoncito, Argentina.

Space Velocities of Southern Globular Clusters. II. New Results for 10 Clusters

Absolute proper motions have been measured for 10 clusters, in addition to the sample of five clusters presented in an earlier paper. These newly measured clusters are NGC 1904 (M79), NGC 2298, NGC 4590 (M68), NGC 5139 (ω Cen), NGC 5897, NGC 6093 (M80), NGC 6121 (M4), NGC 6144, NGC 6809 (M55), and NGC 7099 (M30). The correction to absolute proper motion is determined based on galaxies, except for one field with high extinction, for which we used the Hipparcos system. This latter correction proves to be very useful for fields at low Galactic latitude, provided magnitude-dependent systematics are well controlled. The errors in absolute proper motion per cluster range between 0.4 and 1.0 mas yr-1. Space velocities are also determined, and the kinematics are briefly discussed; a companion paper will present a detailed analysis of orbits in conjunction with other physical parameters of clusters.

PROPER-MOTION STUDY OF THE MAGELLANIC CLOUDS USING SPM MATERIAL

Resumen en: Absolute proper motions are determined for stars and galaxies to V = 17.5 over a 450 square degree area that encloses both Magellanic Clouds. The proper ...

Velocity Shear of the Thick Disk from SPM3 Proper Motions at the South Galactic Pole

The kinematical properties of the Galactic thick disk are studied using absolute proper motions from the Third Yale/San Juan Southern Proper Motion Catalog and Two Micron All Sky Survey near-infrared photometry for a sample of ~1200 red giants in the direction of the south Galactic pole. The photometrically selected sample is dominated by thick-disk stars, as indicated by the number-density distribution that varies with distance from the Galactic plane as a single-valued exponential over the range 1 kpc < z < 4 kpc. The inferred scale height of the thick disk is 0.783 ± 0.048 kpc. The kinematics of the sample are also consistent with disklike motion. The U-velocity component is roughly constant, reflecting the Suns peculiar motion, while a considerable shear is seen in the mean rotational velocity, V. The V-velocity profiles dependence on z is linear, with a gradient of dV/dz = -30 ± 3 km s-1 kpc-1. The velocity dispersions in both U and V show a lesser gradient of about 9 ± 3 km s-1 kpc-1. We demonstrate that the derived velocity and velocity-dispersion profiles are consistent with the assumptions of dynamical equilibrium and reasonable models of the overall Galactic potential.

SPACE VELOCITIES OF SOUTHERN GLOBULAR CLUSTERS. VII. NGC 6397, NGC 6626 (M28), AND NGC 6656 (M22)

We have measured the absolute proper motions of globular clusters NGC 6397, NGC 6626 (M22), and NGC 6656 (M28) as part of our ongoing Southern Proper-Motion Program. The reference system is the ICRS via Hipparcos stars for these three low-Galactic-latitude clusters. Formal errors range between {approx}0.3 and 0.7 mas yr{sup -1}. Notable is the result for NGC 6397, which differs by 2.5 mas yr{sup -1} from two Hubble Space Telescope determinations while agreeing with previous ground-based ones. We determine orbits for all three clusters in an axisymmetric and barred model of the Galaxy and discuss these in the context of globular-cluster formation. M22 is a well-known cluster with an iron abundance spread; such clusters are now believed to have formed in massive parent systems that can retain ejecta of core-collapsed supernovae. We find that the five currently accepted globular clusters with iron/calcium abundance spread show orbits unrelated to each other, thus suggesting at least five independent, massive progenitors that have contributed to the build-up of the Milky-Way halo.

SPACE VELOCITIES OF SOUTHERN GLOBULAR CLUSTERS. IV. FIRST RESULTS FOR INNER GALAXY CLUSTERS

We have measured the absolute proper motions of four low-latitude, inner Galaxy globular clusters. These clusters are NGC 6266 (M62), NGC 6304, NGC 6316, and NGC 6723. The proper motions are on the Hipparcos system, since no background extragalactic objects are found in these high-extinction regions. The proper-motion uncertainties range between 0.3 and 0.6 mas yr � 1 . We discuss the kinematics of these clusters and of three additional bulge clusters—NGC 6522, NGC 6528, and NGC 6553—whose proper motions with respect to bulge stars had been determined previously. We find that all of the clusters have velocities that confine them to the bulge region. Of the three metal-poor clusters ([Fe/H] < � 1.0), NGC 6522, and NGC 6723 have kinematics consistent with halo membership. The third cluster, NGC 6266 however, appears to belong to a rotationally supported system. Of the four metal-rich clusters ([Fe/H] �� 1.0), NGC 6304 and NGC 6553 also have kinematics consistent with membership to a rotationally supported system. NGC 6528 has kinematics, metallicity, and mass that argue in favor of a genuine Milky Way bar cluster. NGC 6316’s kinematics indicate membership to a hotter system than the bar.

SPACE VELOCITIES OF SOUTHERN GLOBULAR CLUSTERS. VI. NINE CLUSTERS IN THE INNER MILKY WAY

(abridged) We have measured the absolute proper motions of nine low-latitude, inner Galaxy globular clusters, namely NGC 6273 (M 19), NGC 6284, NGC 6287, NGC 6293, NGC 6333 (M 9), NGC 6342, NGC 6356, NGC 6388 and NGC 6441. These are the first determinations ever made for these clusters. The proper motions are on the ICRS via Hipparcos. The proper-motion errors range between 0.4 and 0.9 mas/yr, and are dominated by the number of measurable cluster members in these regions which are very crowded by the bulge/bar and the thick disk. This samle contains five metal poor ([Fe/H < -1.0) and four metal rich clusters; seven clusters are located within 4 kpc from the Galactic center, while the remaining two, namely NGC 6356 and NGC 6284 are in the background of the bulge at 7.5 kpc from the Galactic center. By combining proper motions with radial velocities and distances from the literature we derive 3D velocities. In a number of cases, distance uncertainties make the kinematical classification ambiguous. The two metal rich clusters NGC 6388 and NGC 6441 have velocities incompatibile with membership in the thick disk or the bar of the Milky Way. They can be though of as members of a kinematically hot system in the inner Galaxy. Curiously, both clusters have similar velocity components. Together with their similar Galactic location and peculiar but similar stellar-population characteristics, these two clusters may share a common origin. Their velocities are also very low indicating that the two clusters are now at/near apocenter, and they will not leave the inner ~4 kpc of the Galaxy.

The Southern Proper Motion Program. III. A Near-Complete Catalog to V = 17.5

We present the third installment of the Yale/San Juan Southern Proper Motion Catalog, SPM3. Absolute proper motions, positions, and photographic BV photometry are given for roughly 10.7 million objects, primarily stars, down to a magnitude of V = 17.5. The catalog covers an irregular area of 3700 deg2, between the declinations of -20? and -45?, excluding the Galactic plane. The proper-motion precision for well-measured stars is estimated to be 4.0 mas yr-1. Unlike previous releases of the SPM Catalog, the proper motions are on the International Celestial Reference System by way of Hipparcos catalog stars and have an estimated systematic uncertainty of 0.4 mas yr-1. The SPM3 Catalog is available via electronic transfer. As an example of the potential of the SPM3 proper motions, we examine the Galactocentric velocities of a group of metal-poor, main-sequence A stars. The majority of these exhibit thick-disk kinematics, lending support to their interpretation as thick-disk blue stragglers, as opposed to being an accreted component.