Оглавление
Изображения
Загрузить ваше изображение
DSS Images Other Images
Публикации по объекту
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.
| 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.
| Neutral hydrogen profiles of cluster galaxies
Neutral hydrogen profiles of 67 galaxies in seven nearby clusters havebeen obtained with the Arecibo telescope. The neutral hydrogen masses ofthese galaxies range from 2 x 108 to 2 x 1010 M.There is no evidence for significant neutral hydrogen deficiency in anyof these clusters.
| The velocity field of clusters of galaxies within 100 megaparsecs. II - Northern clusters
Distances and peculiar velocities for galaxies in eight clusters andgroups have been determined by means of the near-infrared Tully-Fisherrelation. With the possible exception of a group halfway between us andthe Hercules Cluster, we observe peculiar velocities of the same orderas the measuring errors of about 400 km/s. The present sample is drawnfrom the northern Galactic hemisphere and delineates a quiet region inthe Hubble flow. This contrasts with the large-scale flows seen in theHydra-Centaurus and Perseus-Pisces regions. We compare the observedpeculiar velocities with predictions based upon the gravity fieldinferred from the IRAS redshift survey. The differences between theobserved and predicted peculiar motions are generally small, except neardense structures, where the observed motions exceed the predictions bysignificant amounts. Kinematic models of the velocity field are alsocompared with the data. We cannot distinguish between parameterizedmodels with a great attractor or models with a bulk flow.
| Galaxies possibly resembling M82-type galaxies
A list of 298 galaxies with possible features of M82 galaxies ispresented. This list contains those Irr II candidates whose images onPalomar photographs shown no trace of dust although the objects are redand suspected to be peculiar.
| Near-infrared observations of galaxies in the Coma supercluster
Near-IR magnitudes have been obtained for 136 galaxies in the Coma/A1367supercluster region, and near-IR colors (J-H) and (H-K) for 90 and 87objects, respectively. The near-IR colors are contained in a small rangeand do not depend on morphological types, galaxy inclination, orenvironment. Optical-to-IR colors depend strongly on a galaxy'smorphological type and inclination. There is a dependence of therelative excess of radio, and to a lesser degree, of far-IR emission onrecent star formation activity. The magnitude-line width relation forgalaxies in Coma and A1367 obtained with these data has a larger spreadthan previously found with smaller samples. The data suggest a distancemodulus to Coma of about 35, regardless of the choice of primarycalibrators.
| The NGC 4005 group - A rotating system of galaxies?
H I line observations with the Arecibo 305 m telescope were made of 23galaxies within a 7 square degree region centered on the NGC 4005 group,a system of galaxies located in Zw 127-10. Accurate radial velocitiesand direct mass estimates derived from the 21 cm line profiles of thegalaxies in this region are reported. A systematic trend in the radialvelocities is found along the major axis of the NGC 4005 group. Thiscorrelation between position and velocity is fitted to a simple linearregression relation with a slope significantly different from zero. Oneexplanation for this effect is that the NGC 4005 group is rotating witha period no longer than four billion yr. Other possible interpretationsof this systematic effect are discussed. The mass of the group isestimated by applying the harmonic law, the virial theorem, and theprojected mass method. The masses obtained from the three methods areall consistent.
| Radio continuum survey of the Coma/A1367 supercluster. I - 610 MHz observations of CGCG galaxies in four groups
Radio continuum observations obtained with the Westerbork RadioSynthesis Telescope (WSRT) at 0.6 GHz of four groups of galaxies in theComa/A1367 supercluster area are presented. Ninety-nine CGCG galaxieswere surveyed, yielding the detection of 21 objects. A wide-angle-tailradio galaxy, NGC 4061, in the NGC 4065 group is found. Analysis of thissource suggests a relatively low value (n(e) T approximately 1000 per cucm K) for the intracluster gas pressure in this group.
|
Добавить новую статью
Внешние ссылки
- - Внешних ссылок не найдено -
Добавить внешнюю ссылку
Группы:
|
Наблюдательные данные и астрометрия
Каталоги и обозначения:
|
