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Objective Classification of Spiral Galaxies Having Extended Rotation Curves Beyond the Optical Radius
We carry out an objective classification of four samples of spiralgalaxies having extended rotation curves beyond the optical radius. Amultivariate statistical analysis (viz., principal component analysis[PCA]) shows that about 96% of the total variation is due to twocomponents, one being the combination of absolute blue magnitude andmaximum rotational velocity beyond the optical region and the otherbeing the central density of the halo. On the basis of PCA a fundamentalplane has been constructed that reduces the scatter in the Tully-Fisherrelation up to a maximum of 16%. A multiple stepwise regression analysisof the variation of the overall shape of the rotation curves shows thatit is mainly determined by the central surface brightness, while theshape purely in the outer part of the galaxy (beyond the optical radius)is mainly determined by the size of the galactic disk.
| Arcsecond Positions of UGC Galaxies
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
| An Einstein X-Ray Survey of Optically Selected Galaxies. I. Data
We present the results of a complete Einstein imaging proportionalcounter X-ray survey of optically selected galaxies from theShapley-Ames Catalog, the Uppsala General Catalogue, and the EuropeanSouthern Observatory Catalog. Well-defined optical criteria are used toselect the galaxies, and X-ray fluxes are measured at the opticallydefined positions. The result is a comprehensive list of X-ray detectionand upper limit measurements for 1018 galaxies. Of these, 827 haveeither independent distance estimates or radial velocities. Associatedoptical, redshift, and distance data have been assembled for thesegalaxies, and their distances come from a combination of directlypredicted distances and those predicted from the Faber-Burstein GreatAttractor/Virgocentric infall model. The accuracy of the X-ray fluxeshas been checked in three different ways; all are consistent with thederived X-ray fluxes being of <=0.1 dex accuracy. In particular,there is agreement with previously published X-ray fluxes for galaxiesin common with a 1991 study by Roberts et al. and a 1992 study byFabbiano et al. The data presented here will be used in further studiesto characterize the X-ray output of galaxies of various morphologicaltypes and thus to enable the determination of the major sourcescontributing to the X-ray emission from galaxies.
| ASCA Observation of the Rapid Burster in Quiescence
We observed the Rapid Burster in quiescence and detected a significantX-ray flux for the first time. Neither a type-I nor type-II burst wasobserved during the observation. The luminosity was estimated to be(3(+2}_{-1) )times 10(33) erg s(-1) ( 2--10 keV), assuming a power-lawwith a photon index of 2 and a distance of 10 kpc. This luminosity iscomparable to that of neutron-star transients in quiescence. If massaccretion is responsible for the X-ray emission, we can constrain themagnetic-field strength and spin period of the neutron star. A highlymagnetized, rapidly rotating neutron star may be excluded.
| HI observations of galaxies in nearby Zwicky clusters
The results of a long term project of H I observations of galaxieswithin the boundaries of nearby Zwicky clusters are presented. Thedetection rate is rather low (233 out of 618, i.e., 38 percent) ascompared to other surveys carried out recently. Most of the radialvelocities of the detected galaxies are new determinations. The largespread in radial velocities for many of these clusters is a strongindication for the presence of several foreground and/or backgroundgalaxies.
| The globular cluster system of the Galaxy. II - The spatial and metallicity distributions, the second parameter phenomenon, and the formation of the cluster system
Metal abundance measurements that were made for 84 globular clusters areused to describe the cluster system of the Galaxy. There is a metalabundance gradient between the clusters within 9 kpc of the galacticcenter and the clusters more distant than 9 kpc. There is a metalabundance gradient with distance from the galactic plane among theclusters within 9 kpc of the galactic center. The strength of the secondparameter phenomenon varies systematically with galactocentric distance;hence regardless of whether this phenomenon is caused by age orcomposition variations, it is related to the large-scale evolution ofthe Galaxy. If age is the second parameter, then the outer halo clustersformed later over a longer period of time than the metal-poor clustersin the inner halo.
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