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The Velocity Dispersion Profile of the Remote Dwarf Spheroidal Galaxy Leo I: A Tidal Hit and Run?
We present new kinematic results for 387 stars near the Milky Waysatellite dwarf spheroidal galaxy Leo I. Spectra were obtained with theHectochelle multiobject echelle spectrograph on the MMT, centered in theoptical near 5200 Å. From 297 repeat measurements of 108 stars, weestimate the mean velocity error (1 ?) of our sample to be 2.4 kms-1, with a systematic precision of <=1 km s-1.The final sample of 328 Leo I members gives a mean heliocentric velocityof 282.9+/-0.5 km s-1 and a dispersion of 9.2+/-0.4 kms-1. The dispersion profile of Leo I is flat to beyond itsclassical ``tidal'' radius. We fit the profile to various equilibriumdynamical models. We strongly rule out all models where mass followslight. Anisotropic Sérsic+NFW models fit the dispersion profilewell, but isotropic models are ruled out at a 95% confidence level.Inside a projected radius of ~1040 pc, the mass and V-band mass-to-lightratio of Leo I from equilibrium models are in the ranges(5-7)×107 Msolar and 9-14 (solar units),respectively. Leo I members outside a ``break radius'' ofRb~400'' (500 pc) exhibit significant velocityanisotropy, whereas stars interior to this radius are consistent with anisotropic velocity distribution. We interpret the break radius as thetidal radius of Leo I at perigalacticon some 1-2 Gyr ago. Thisinterpretation accounts for the complex star formation history of Leo I,population segregation within the galaxy, and Leo I's large outwardgalactocentric velocity. The lack of evident tidal arms in Leo Isuggests that the galaxy may have been injected into its present highlyelliptical orbit by a third body a few Gyr before its lastperigalacticon. This scenario is plausible within current hierarchicalstructure formation models.
| Constant-Velocity Stars at the North Galactic Pole Suitable for Use as Secondary Velocity Standards
We present mean radial velocities for 143 stars in Selected Area 57 atthe north Galactic pole that are suitable for use as secondary velocitystandards. The stars were drawn from a magnitude-limited sample and aremostly fainter than 11th magnitude in V. They span a wide range ofeffective temperatures and surface gravities and thus provide a suitablesource of targets for observed templates. The mean radial velocities arebased on at least 10 observations spanning at least 8200 days, and areaccurate typically to 0.2 km s-1, with no obvious signs ofvariable velocity or composite spectra.Some of the results presented here used observations made with the MMT,a joint facility of the Smithsonian Institution and the University ofArizona.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Kinematics of NGC 2264: Signs of Cluster Formation
We present results from 1078 high-resolution spectra of 990 stars in theyoung open cluster NGC 2264, obtained with the Hectochelle multiobjectechelle spectrograph on the 6.5 m MMT. We confirm 471 stars as memberson the basis of their radial velocity and/or H? emission. Theradial velocity distribution of cluster members is non-Gaussian, with adispersion of ?~3.5 km s-1. We find a substantialnorth-south velocity gradient and spatially coherent structure in theradial velocity distribution, similar to that seen in the molecular gasin the region. Our results suggest that there are at least threedistinguishable subclusters in NGC 2264, correlated with similarstructure seen in 13CO emission, which is likely to be aremnant of initial structure in this very young cluster. We propose thatthis substructure is the result of gravitational amplification ofinitial inhomogeneities during overall collapse to a filamentarydistribution of gas and stars, as found in simulations by Burkert &Hartmann (2004).Observations reported here were obtained at the MMT Observatory, a jointfacility of the Smithsonian Institution and the University of Arizona.
| A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)
The LSPM catalog is a comprehensive list of 61,977 stars north of theJ2000 celestial equator that have proper motions larger than 0.15"yr-1 (local-background-stars frame). The catalog has beengenerated primarily as a result of our systematic search for high propermotion stars in the Digitized Sky Surveys using our SUPERBLINK software.At brighter magnitudes, the catalog incorporates stars and data from theTycho-2 Catalogue and also, to a lesser extent, from the All-SkyCompiled Catalogue of 2.5 million stars. The LSPM catalog considerablyexpands over the old Luyten (Luyten Half-Second [LHS] and New LuytenTwo-Tenths [NLTT]) catalogs, superseding them for northern declinations.Positions are given with an accuracy of <~100 mas at the 2000.0epoch, and absolute proper motions are given with an accuracy of ~8 masyr-1. Corrections to the local-background-stars propermotions have been calculated, and absolute proper motions in theextragalactic frame are given. Whenever available, we also give opticalBT and VT magnitudes (from Tycho-2, ASCC-2.5),photographic BJ, RF, and IN magnitudes(from USNO-B1 catalog), and infrared J, H, and Ks magnitudes(from 2MASS). We also provide an estimated V magnitude and V-J color fornearly all catalog entries, useful for initial classification of thestars. The catalog is estimated to be over 99% complete at high Galacticlatitudes (|b|>15deg) and over 90% complete at lowGalactic latitudes (|b|>15deg), down to a magnitudeV=19.0, and has a limiting magnitude V=21.0. All the northern starslisted in the LHS and NLTT catalogs have been reidentified, and theirpositions, proper motions, and magnitudes reevaluated. The catalog alsolists a large number of completely new objects, which promise to expandvery significantly the census of red dwarfs, subdwarfs, and white dwarfsin the vicinity of the Sun.Based on data mining of the Digitized Sky Surveys (DSSs), developed andoperated by the Catalogs and Surveys Branch of the Space TelescopeScience Institute (STScI), Baltimore.Developed with support from the National Science Foundation (NSF), aspart of the NASA/NSF NStars program.
| The Pul-3 catalogue of 58483 stars in the Tycho-2 system
A catalogue of positions and proper motions of 58483 stars (Pul-3) hasbeen constructed at the Pulkovo observatory. The Pul-3 is based on theresults of measurements of photographic plates with galaxies (Deutsch'splan). All plates were taken using the Pulkovo Normal Astrograph (thefirst epoch is in the 1950s and the second epoch is in the 1970s).The Pul-3 catalogue contains stars of mainly 12 to 16.5 mag in 146fields with galaxies in the declination zone from -5o to+85o. The Tycho-2 has been used as a reference catalogue.The mean epoch of the Pul-3 is 1963.25. The internal positional accuracyof the Pul-3 catalogue at the mean epoch of observations is ±80mas. The accuracy of the proper motions is mostly within ±3mas/yr to ±12 mas/yr. Comparisons of the Pul-3 with Tycho-2 andARIHIP have been done at the mean epoch of the Pul-3. The Pul-3 externalpositional accuracy relative to Tycho-2 is ±150 mas.The catalogue is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/357
| Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog
We complete construction of a catalog containing improved astrometry andnew optical/infrared photometry for the vast majority of NLTT starslying in the overlap of regions covered by POSS I and by the secondincremental Two Micron All Sky Survey (2MASS) release, approximately 44%of the sky. The epoch 2000 positions are typically accurate to 130 mas,the proper motions to 5.5 mas yr-1, and the V-J colors to0.25 mag. Relative proper motions of binary components are measured to 3mas yr-1. The false-identification rate is ~1% for11<~V<~18 and substantially less at brighter magnitudes. Theseimprovements permit the construction of a reduced proper-motion diagramthat, for the first time, allows one to classify NLTT stars intomain-sequence (MS) stars, subdwarfs (SDs), and white dwarfs (WDs). We inturn use this diagram to analyze the properties of both our catalog andthe NLTT catalog on which it is based. In sharp contrast to popularbelief, we find that NLTT incompleteness in the plane is almostcompletely concentrated in MS stars, and that SDs and WDs are detectedalmost uniformly over the sky δ>-33deg. Our catalogwill therefore provide a powerful tool to probe these populationsstatistically, as well as to reliably identify individual SDs and WDs.
| A search for wide binaries at the north galactic pole using precise radial velocities
Precise radial velocities are presented from a survey of 247 starscentered on Selected Area 57 at the North Galactic Pole, complete forlate-type stars with V magnitude brighter than 12.0. The radialvelocities have a typical precision of 0.2-0.3 km/s. New spectral typesand distances estimates are presented for 120 of the stars in thesample. All pairs of stars with angular separations between 1 and 600arcsec have been considered, and 11 candidate pairs found with velocitydifferences less than 1.5 km/s. It is estimated that 4 or 5 of the 11candidate pairs are actually bound binaries, but none with separationslarger than 0.1 pc. The constraints imposed by these results on theactual distribution of wide binaries in the Galaxy should now bereanalyzed. The unusual precision of the velocities led to the discoveryof a new cluster associated with the multiple system ADS 8811 ABC.
| Proper-Motion Surveys with Schmidt Plates - Part One - the North Galactic Pole
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990MNRAS.247...70R&db_key=AST
| Photoelectric V and (B-V) for Weistrop stars near the north Galactic pole
V and (B-V) have been obtained for 173 stars near the north Galacticpole. A comparison is made between these photoelectric values and thephotographic values obtained by Weistrop (1972). Corrections have beenderived which, when applied to (B-V)w and Vw, result in relativelysystematic error-free colors and magnitudes.
| A kinematic and abundance survey at the Galactic poles. III
A sample of 418 space velocities are examined, including 83 new valuesobtained for G5-K6 giants near the North Galactic Pole. A constantDDO-derived Fe/H abundance gradient of about -0.18 dex/kpc is found toextend to 8 kpc. The data show a continuous increase in the velocitydispersion as the distance above the Galactic plane increases and as theDDO-derived Fe/H abundance ratio decreases to -1.00. The data suggest akinematic decoupling of the thick disk and halo stars. As in the case ofthe abundance gradient, the kinematic data are shown to be consistentwith the concept of the galactic-model components. It is noted thatgiants with solar DDO-derived abundances are found only sparsely in thethick disk.
| Photometric parallaxes for selected stars of color class M from the NLTT catalog. III - The declination zone +20 deg to +45 deg
VRI photometry and photometric parallaxes are presented for a sample of787 late-type stars in the NLTT catalog for which no trigonometricparallaxes have been measured. Additional photometry of 108 stars withtrigonometric parallaxes is also presented. For the program stars, 131have pi(ph) of 0.04 arcsec or greater and six of these have pi(ph) of0.10 arcsec or greater. The percentage of subdwarfs among the stars thusfar surveyed is probably less than 3 percent.
| Errata in Magnitudes of Stars in AGK3
Not Available
| Photoelectric Magnitudes and Colors of Stars Near the North Galactic Pole.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1964ApJ...140..151H&db_key=AST
| Photographic photometry at the North galactic Pole.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1956AJ.....61...80S&db_key=AST
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Membre dels grups següents:
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Dades d'Observació i Astrometria
| Constel·lació: | Coma Berenices |
| Ascensió Recta: | 13h06m45.82s |
| Declinació: | +29°46'30.5" |
| Magnitud Aparent: | 11.451 |
| Moviment propi RA: | 26.2 |
| Moviment propi Dec: | -149.1 |
| B-T magnitude: | 12.625 |
| V-T magnitude: | 11.548 |
Catàlegs i designacions:
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