577 research outputs found

    A homogeneous sample of binary galaxies: Basic observational properties

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    A survey of optical characteristics for 585 binary systems, satisfying a condition of apparent isolation on the sky, is presented. Influences of various selection effects distorting the average parameters of the sample are noted. The pair components display mutual similarity over all the global properties: luminosity, diameter, morphological type, mass-to-luminosity ratio, angular momentum etc., which is not due only to selection effects. The observed correlations must be caused by common origin of pair members. Some features (nuclear activity, color index) could acquire similarity during synchronous evolution of double galaxies. Despite the observed isolation, the sample of double systems is seriously contaminated by accidental pairs, and also by members of groups and clusters. After removing false pairs estimates of orbital mass-to-luminosity ratio range from 0 to 30 f(solar), with the mean value (7.8 plus or minus 0.7) f(solar). Binary galaxies possess nearly circular orbits with a typical eccentrity e = 0.25, probably resulting from evolutionary selection driven by component mergers under dynamical friction. The double-galaxy population with space abundance 0.12 plus or minus 0.02 and characteristic merger timescale 0.2 H(exp -1) may significantly influence the rate of dynamical evolution of galaxies

    HI Observations of Flat Galaxies

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    We present the HI observations of 94 flat spiral galaxies from RFGC (the Revised Flat Galaxy Catalog) and 14 galaxies from 2MFGC (the 2MASS selected Flat Galaxy Catalog) performed with the 100-m radio telescope in Effelsberg (Germany). HI fluxes, heliocentric radial velocities, and HI line widths are given for 65 detected galaxies. We present a mosaic of HI profiles. We calculated some of the global parameters of the galaxies and analyzed the linear correlations between them. The ratios of the total (indicative) masses of the galaxies to their luminosities lie within the range 0.4 with a mean of 3.8 (M_{\sun}/L_{\sun}), and the mean mass fraction of neutral hydrogen is 13%. Upper limits are given for the radio fluxes from 43 undetected galaxies.Comment: 24 pages, 7 figure

    HI properties of nearby galaxies from a volume-limited sample

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    We consider global HI and optical properties of about three hundred nearby galaxies with V0<500_0 < 500 km/s. The majority of them have individual photometric distance estimates. The galaxy sample parameters, e.g. their linear diameters, their HI mass-to-luminosity ratio, their total mass-to-luminosity ratio, their mean optical surface brightness show some known and some new correlations implying a meaningful dynamic explanation. For the LV galaxies their HI mass and angular momentum follow a nearly linear relation expected for rotating gaseous disks being near the threashold of gravitational instability, favourable for active star formation.Comment: 5 pages, 9 figures, uses laa.sty accepted by A&A Suppl. Serie
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