H I Observations of Barred Magellanic Spirals. II. The Frequency and Impact of Companions
The results of an H I 21 cm line survey of a sample of Magellanic spiralgalaxies with apparent optical companions reveal that only four of 13systems have confirmed H I-detected neighbors. The current interactionsare affecting the morphology of the main galaxy in only two cases, NGC3664 and NGC 3995. The presence of companions near NGC 2537 and UGC 5391appears to have no effect on the morphology of those galaxies. Overall,there is little difference between the asymmetry of the H I profiles ofthose galaxies with and without companions, and on average, theseMagellanic spirals have H I profiles that are no more asymmetric than arandom sample of spirals in the field. We conclude that currentinteractions cannot be responsible for the lopsided morphology of mostof the galaxies in this sample and that, whatever its original cause,lopsidedness must be a long-lived characteristic of these galaxies.
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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.
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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.
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The CfA Redshift Survey: Data for the NGP +36 Zone
We have assembled redshifts for a complete sample of 719 galaxies withm_zw_ <= 15.5 in the declination range 32.5^deg^ <= δ <=38.5^deg^ and right ascension range 8^h^ <= α <= 17^h^. Wehave determined morphological types for all galaxies in the magnitudelimited sample by direct inspection of the POSS-O plates. 576 of theredshifts are measurements from Mount Hopkins, and 405 are newredshifts. We also include new redshifts for 77 fainter galaxies in thesame strip.
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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.
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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.
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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.
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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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