Contents
Images
Upload your image
DSS Images Other Images
Related articles
Nearby Optical Galaxies: Selection of the Sample and Identification of Groups
In this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation ``friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales.
| A CCD Study of the Environment of Seyfert Galaxies. III. Host Galaxies and the Nearby Environments
A technique is described that permits the robust decomposition of thebulge and disk components of a sample of Seyfert galaxies, as well as a(control) sample of nonactive galaxies matched to the Seyferts in thedistributions of redshift, luminosity, and morphological classification.The structural parameters of the host galaxies in both samples aremeasured. No statistically significant differences at greater than the95% level are found in these parameters according to aKolmogorov-Smirnov test. ``Companion galaxies''-defined as any galaxywithin a projected separation of 200 h-1 kpc from the centerof the host-are identified and their basic properties measured. Acomparison between the active and control samples in the distributionsof apparent R magnitude, absolute R magnitude (assuming the companionsare at the distance of the host), projected separation from the host,position angle relative to the host, magnitude difference between thecompanion and host, and strength of the tidal parameter shows nostatistically significant differences. Similarly, no statisticallysignificant differences are found between the control and active samplehost galaxies in terms of light asymmetries-bars, rings, isophotaltwisting, etc. The implications for a model in which interactions andmergers are responsible for inciting activity in galactic nuclei arediscussed briefly.
| 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.
| A CCD Study of the Environment of Seyfert Galaxies. I. The Survey
Large-format, R-band CCD data are presented for a spectroscopicallycomplete sample of 34 Seyfert galaxies and a control sample of 45nonactive galaxies that are well matched to the Seyfert sample inredshift, luminosity, and morphological type. Gray-scale images of thelocal environment are included for all of the host galaxies, as well asfigures showing the surface brightness, ellipticity, and position angleof the major axis as a function of radius. These data will be used tostudy the environments of these galaxies and hence to test the"interaction hypothesis" that, over the past two decades, has beenimplicated as the triggering mechanism for nuclear activity. While thereare no dramatic differences in most parameters between the active andnonactive samples, the distributions of ellipticities and major-axisposition-angle excursions of the Seyfert host galaxies and the controlgalaxies are marginally different. A higher proportion of Seyfertgalaxies appear to be involved in late-stage mergers. A similar fractionof the control sample, however, displays significant light asymmetriesthat could be evidence for recent interactions. Moreover, a small butsubstantial number of the Seyfert galaxies show no evidence for recentinteractions as judged by the absence of light asymmetries.
| Groups of galaxies. III. Some empirical characteristics.
Not Available
| Kinematics of the local universe. VII. New 21-cm line measurements of 2112 galaxies
This paper presents 2112 new 21-cm neutral hydrogen line measurementscarried out with the meridian transit Nan\c cay radiotelescope. Amongthese data we give also 213 new radial velocities which complement thoselisted in three previous papers of this series. These new measurements,together with the HI data collected in LEDA, put to 6 700 the number ofgalaxies with 21-cm line width, radial velocity, and apparent diameterin the so-called KLUN sample. Figure 5 and Appendices A and B forcorresponding comments are available in electronic form at thehttp://www.edpsciences.com
| 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.
| A revised catalog of CfA1 galaxy groups in the Virgo/Great Attractor flow field
A new identification of groups and clusters in the CfA1 Catalog ofHuchra et al. is presented, using a percolation algorithm to identifydensity enhancements. It is shown that in the resulting catalog,contamination by interlopers is significantly reduced. The Schechterluminosity function is redetermined, including the Malmquist bias.
| General study of group membership. II - Determination of nearby groups
We present a whole sky catalog of nearby groups of galaxies taken fromthe Lyon-Meudon Extragalactic Database. From the 78,000 objects in thedatabase, we extracted a sample of 6392 galaxies, complete up to thelimiting apparent magnitude B0 = 14.0. Moreover, in order to considersolely the galaxies of the local universe, all the selected galaxieshave a known recession velocity smaller than 5500 km/s. Two methods wereused in group construction: a Huchra-Geller (1982) derived percolationmethod and a Tully (1980) derived hierarchical method. Each method gaveus one catalog. These were then compared and synthesized to obtain asingle catalog containing the most reliable groups. There are 485 groupsof a least three members in the final catalog.
| Groups of galaxies within 80 Mpc. II - The catalogue of groups and group members
This paper gives a catalog of the groups and associations obtained bymeans of a revised hierarchical algorithm applied to a sample of 4143galaxies with diameters larger than 100 arcsec and redshifts smallerthan 6000 km/s. The 264 groups of galaxies obtained in this way (andwhich contain at least three sample galaxies) are listed, with the looseassociations surrounding them and the individual members of eachaggregate as well; moreover, the location of every entity among 13regions corresponding roughly to superclusters is specified. Finally,1729 galaxies belong to the groups, and 466 to the associations, i.e.,the total fraction of galaxies within the various aggregates amounts to53 percent.
| Observational data for the kinematics of the local universe. I - Radial velocity measurements
The study of the local velocity field requires the use of a very largesample to describe as accurately as possible some prominent features ofthe local kinematics. The problem of collecting a large sample is mademore difficult because of the Malmquist bias which plagues distancedeterminations. The present program aims at determining bias-freedistances for a complete sample in order to study the local velocityfield. The present paper gives 303 preliminary optical and radioredshifts measured for this program at ESO, OHP and NancayObservatories.
| The far-infrared properties of the CfA galaxy sample. I - The catalog
IRAS flux densities are presented for all galaxies in the Center forAstrophysics magnitude-limited sample (mB not greater than 14.5)detected in the IRAS Faint Source Survey (FSS), a total of 1544galaxies. The detection rate in the FSS is slightly larger than in thePSC for the long-wavelength 60- and 100-micron bands, but improves by afactor of about 3 or more for the short wavelength 12- and 25-micronbands. This optically selected sample consists of galaxies which are, onaverage, much less IR-active than galaxies in IR-selected samples. Itpossesses accurate and complete redshift, morphological, and magnitudeinformation, along with observations at other wavelengths.
| Cosmology from a galaxy group catalog. I - Binaries
A new, completely objective group-finding algorithm is described andapplied to the CfA redshift catalog. The binary galaxies are isolatedfor analysis. The assumptions underlying the analysis are (1) that lighttraces mass, (2) that our binary galaxy subsets are representative lighttracers, and (3) that the binary orbits are circular. The primary resultof the work is that the resulting bias-free binary catalogs are afunction of the assumed cosmological model. For virtually any inputvalue of Omega(0) in the range 0.01-5.00, there is a reasonablyconsistent interpretation of the CfA survey such that the specifiedvalue of Omega(0) can be derived from the binary sample obtained underthat interpretation. A secondary result is that the higher the inputvalue of Omega(0), the broader the intrinsic distribution in M/L, andhence the less valid the assumption that light traces mass.
| Arm classifications for spiral galaxies
The spiral arm classes of 762 galaxies are tabulated; 636 galaxies withlow inclinations and radii larger than 1 arcmin were classified on thebasis of their blue images on the Palomar Observatory Sky Survey (POSS),76 SA galaxies in the group catalog of Geller and Huchra were alsoclassified from the POSS, and 253 galaxies in high-resolution atlaseswere classified from their atlas photographs. This spiral armclassification system was previously shown to correlate with thepresence of density waves, and galaxies with such waves were shown tooccur primarily in the densest galactic groups. The present sampleindicates, in addition, that grand design galaxies (i.e., those whichtend to contain prominent density wave modes) are physically larger thanflocculent galaxies (which do not contain such prominent modes) by afactor of about 1.5. A larger group sample confirms the previous resultthat grand design galaxies are preferentially in dense groups.
| The radial distribution of surface brightness in galactic disks
Surface photometry of 51 galaxies based on a number of deeply exposedIIIa-J Schmidt plates, is reported. A sample of spiral galaxies that iscomplete to a diameter of 2 arcmin at the apparent isophote of 26.5J-mag per square arcsecond has a narrow distribution of central surfacebrightness with mu0 = 21.8 plus or minus 0.6 J-mag per squarearcsecond (mean and standard deviation). This is not produced by sampleselection effects. The bivariate distribution function of mu0and scalelength h shows that the mean value of mu0 changesfrom about 21.5 at h approximately equal to 5 kpc to about 22-22.5 at anh of about 1 kpc. The small spread in mu0 in the universe isprobably a result of a constant ratio of visible to dark matter in allgalaxies, if galaxies collapse with detailed conservation of angularmomentum from uniformly rotating, uniform spheres that derive theirangular momentum from tidal torques in a universe with hierarchicalclustering. This model also explains the approximate exponential natureand the cutoffs in stellar disks at about 4.5 scalelengths.
| A search for environmental effects on the optical properties of galaxies in groups
Environmental density-related modifications of basic optical properties(luminosities, sizes, axial ratios, and colors) of galaxies belonging toGeller and Huchra's (1983) groups have been investigated. Remarkably, itis found that the broad maxima of the distributions of luminosities anddiameters of spirals and the whole corresponding distributions oflenticulars tend to move to lower values as one goes to groups of highcompactness, whereas the luminosity-diameter relationship of spiralstends to become flatter. No color and axial ratio differences betweengalaxies of high- and low-compactness groups have been detected.
| 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.
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
Catalogs and designations:
|
