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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 image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
| Probing the age of elliptical galaxies.
In this paper we address the question whether age and metallicityeffects can be disentangled with the aid of the broad-band colours andspectral indices from absorption feature strengths, so that the age ofelliptical galaxies can be inferred. The observational data underexamination are the indices Hbeta_ and [MgFe] , and thevelocity dispersion {SIGMA} for the sample of galaxies of Gonzales(1993), supplemented by the ultra-violet data, i.e. the colour (1550-V),of Burstein et al. (1988). The analysis is performed with the aid ofchemo-spectro-photometric models of elliptical galaxies with infall ofprimordial gas (aimed at simulating the collapse phase of galaxyformation) and the occurrence of galactic winds. The galaxy models arefrom Tantalo et al. (1995). The study consists of four parts. In thefirst one, the aims are outlined and the key data are presented. In thesecond part, we summarize the main properties of the infall models thatare relevant to our purposes. In the third part we present the detailedcalculations of the spectral indices for single stellar populations andmodel galaxies. To this aim, we use the analytical relations of Wortheyet al. (1994) who give index strengths as a function of stellarparameters. In the last part, we examine the age-metallicity problem. Incontrast with previous interpretations of the Hbeta_ and[MgFe] data as a sort of age sequence (Gonzales 1993), we find that thesituation is more complicate when the space of the four variablesHbeta_, [MgFe] , (1550-V), and {SIGMA} is examined. Galaxiesin the Hbeta_ and [MgFe] plane do not follow a pure sequenceeither of age or metallicity. The observed (1550-V) colours are notcompatible with young ages. Basically, all the galaxies in the sampleare old objects (say as old as 13/15Gyr) but have suffered fromdifferent histories of star formation. Specifically, it seems that somegalaxies have exhausted the star forming activity at very early epochswith no significant later episodes. Others have continued to form starsfor long periods of time. This is perhaps sustained by the analysis ofthe gradients in the Hbeta_ and [MgFe] indices across thegalaxies. There are galaxies with no age difference among the variousregions. There are other galaxies in which large gradients in the meanage of the star forming activity between the central and the peripheralregions seem to exist. The nucleus turns out to be younger and moremetal-rich than the outer regions. Finally, there are galaxies in whichthe nucleus is older but less metal-rich than the external regions. Allthis perhaps hints not only different histories of star formation butalso different mechanisms of galaxy formation difficult to pin down atthe present time. From the analysis of the Hbeta_, [MgFe] ,(1550-V), and {SIGMA} space, and of the age and metallicity gradients insingle galaxies, the suggestion is advanced that the overall duration ofthe star forming activity is inversely proportional to the velocitydispersion {SIGMA} (and perhaps galactic mass).
| The fundamental plane of early-type galaxies: stellar populations and mass-to-light ratio.
We analyse the residuals to the fundamental plane (FP) of ellipticalgalaxies as a function of stellar-population indicators; these are basedon the line-strength parameter Mg_2_ and on UBVRI broad-band colors, andare partly derived from new observations. The effect of the stellarpopulations accounts for approximately half the observed variation ofthe mass-to-light ratio responsible for the FP tilt. The residual tiltcan be explained by the contribution of two additional effects: thedependence of the rotational support, and possibly that of the spatialstructure, on the luminosity. We conclude to a constancy of thedynamical-to-stellar mass ratio. This probably extends to globularclusters as well, but the dominant factor would be here the luminositydependence of the structure rather than that of the stellar population.This result also implies a constancy of the fraction of dark matter overall the scalelength covered by stellar systems. Our compilation ofinternal stellar kinematics of galaxies is appended.
| A Catalog of Stellar Velocity Dispersions. II. 1994 Update
A catalog of central velocity dispersion measurements is presented,current through 1993 September. The catalog includes 2474 measurementsof 1563 galaxies. A standard set of 86 galaxies is defined, consistingof galaxies with at least three reliable, concordant measurements. It issuggested that future studies observe some of these standard galaxies sothat different studies can be normalized to a consistent system. Allmeasurements are reduced to a normalized system using these standards.
| A dynamical analysis of twelve clusters of galaxies
Four-hundred-twenty-eight new redshift measurements for galaxies in thevicinity of 12 Abell clusters are presented. The data are supplementedby previously published data with 3 deg of each cluster center. Thecluster selection, the variety of telescopes and instrumentation used toobtain the galaxy redshifts, and the available X-ray observations arediscussed. Each cluster is exmained in some detail, with the emphasisplaced on the nature of the observed velocity distributions. Robust andresistant estimators of the velocity location and scale are applied inorder to quantify these distributions. The offset in velocity space ofthe dominant galaxy in each cluster or subcluster is considered withrespect to the central location in the velocity space of the cluster asa whole, and the physical implications of significant offsets found inseveral clusters are discussed. Dynamical estimates of the masses ofclusters and/or subclusters are obtained; for clearly bimodal systems,two-body models are employed to specify their likely dynamical state.
| Polarized radio emission from NGC 4945
Observations at 4.75 GHz of the large southerm edge-on spiral galaxy NGC4945 with the Parkes 64-m telescope are reported. The galaxy exhibits anunusual distribution of linearly polarized radio emission: two maxima ofpolarized emission are located at about 2.4 kpc z-distance (on eitherside of the plane of the galaxy), with the line joining them passing theactive center at an angle of about 40 deg with respect to the z-axis.These maxima are reminiscent of the peculiar features seen in the spiralgalaxy NGC 4258 (with medium angular resolution) which is famous for itsanomalous radio arms.
| Individual and orbital masses of double galaxies
A list is given of individual estimates of the masses of 124 componentsof isolated pairs of galaxies from Turner's catalog for which there arepublished data on the velocity dispersions in the central parts of thegalaxies, on the width of the 21-cm radio line profile, and on theamplitude of the rotation curve of the galaxies. From the comparison ofthe orbital estimates of the mass with the sum of the individual massesof the double galaxies it is concluded that the bulk of the mass of thegalaxies is situated within their standard optical diameter A(25). Theconsidered observational data for the Turner galaxy pairs do not containany arguments for the hypothesis of massive halos. Good agreementbetween the orbital and individual estimates of the mass is observed foralmost circular motions of the galaxies in pairs with mean orbitaleccentricity 0.25.
| A catalog of stellar velocity dispersions. I - Compilation and standard galaxies
A catalog of central stellar velocity dispersion measurements ispresented, current through June 1984. The catalog includes 1096measurements of 725 galaxies. A set of 51 standard galaxies is definedwhich consists of galaxies with at least three reliable, concordantmeasurements. It is suggested that future studies observed some of thesestandard galaxies in the course of their observations so that differentstudies can be normalized to the same system. Previous studies arecompared with the derived standards to determine relative accuracies andto compute scale factors where necessary.
| An observational study of the dynamics of binary galaxies
The single velocity measurement rms error value in the present set ofradial velocities for all galaxies in the Turner (1976) catalog of 156binary systems is estimated t be 29 km/sec. Typical velocity differencesare very small, with half of the 55 systems in the subsample of isolatedspiral-spiral pairs (the most reliable set of 'pure' binaries) havingmeasured velocity differences of less than 75 km/sec. By means of MonteCarlo simulations of scale-free ensembles of binary galaxies, it ispossible to show that the present data's independence of eitherluminosity or projected separation is inconsistent both with thehypothesis that the mass of binary systems increases linearly withluminosity, and that galaxies in pairs may effectively be treated aspoint masses. The data favor models in which galaxies interact through aquasi-isothermal potential only weakly depending on luminosity.
| A survey of galaxy redshifts. IV - The data
The complete list of the best available radial velocities for the 2401galaxies in the merged Zwicky-Nilson catalog brighter than 14.5mz and with b (II) above +40 deg or below -30 deg ispresented. Almost 60 percent of the redshifts are from the CfA surveyand are accurate to typically 35 km/s.
| Binary galaxie. I. A well-defined statistical sample.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976ApJ...208...20T&db_key=AST
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