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Diffuse X-Ray Emission in Three Poor Clusters of Galaxies
We report on ROSAT PSPC soft X-ray observations of three poor clustersof galaxies at distances above 100 Mpc (cz>8000 km s-1). Inall three cases the emission is centered on the dominant member of thecluster, i.e., NGC 4104, NGC 6269, and NGC 6329, respectively. X-rayemission was detected out to radii of 400-600 kpc. The bolometric X-rayluminosities range from 2.6 to 8.6x1042 ergs s-1.The soft X-ray emission characteristics and the physical propertiesdeduced from our observations of all three poor clusters resemble thoseof downscaled rich clusters. In each case, the soft X-ray spectrum iswell represented by a thermal model with kT~=1.1-1.3 keV and near-solarmetallicity in the center, increasing to kT~=1.4-1.6 keV toward theouter boundaries while the metallicity, Z, decreases to about 0.1 solar.Equally good fits can be achieved if the metallicity is left at thesolar value and an additional gas component with kT~=0.5 keV isintroduced. The central electron densities in all three poor clustersstudied here are enhanced with respect to a King profile by factors of2-6. This, together with the results of the spectral fits, can beinterpreted as either indicating the presence of cooling flows or of atwo-phase medium in the central areas. The spatial electron densitydistribution in the outer regions of each cluster can be fitted by Kingprofiles with core radii of 17-60 kpc and exponents of β=0.38-0.44.Using the derived radial temperature and density distributions, thetotal gravitating mass is obtained. We deriveMtot=3.7+/-0.7x1013 Msolar within aradius of 300 kpc for each of the three systems, as opposed to1014-1015 Msolar for rich clusters. Wefind that the LX versus kT relation found by A. C. Edge andG. C. Stewart (1991) for rich clusters of galaxies scales into thedomain of poor clusters and groups of galaxies. The spectral fits of thecentral regions show that none of the first-ranking galaxies of thethree poor clusters hosts a Seyfert 1 active galactic nucleus thatcontributes significantly to the emission in the ROSAT band (0.1-2.4keV).
| 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.
| Large-Scale Structure at Low Galactic Latitude
We have extended the CfA Redshift Survey to low galactic latitudes toinvestigate the relation between the Great Wall in the North GalacticCap and the Perseus-Pisces chain in the South Galactic Cap. We presentredshifts for 2020 galaxies in the Catalogue of Galaxies and of Clustersof Galaxies (Zwicky et al. 1961-68, CGCG) in the following regions: 4^h^<= α <= 8^h^, 17^h^ <= α <= 20^h^, 0^deg^ <=δ <= 45^deg^. In these regions, the redshift catalogue includes1664 galaxies with B(0) <= 15.5 (of which 820 are newly measured) andis 97% complete. We also include redshifts for an additional 356galaxies in these regions with B(O) > 15.5; of these, 148 werepreviously unmeasured. The CGCG samples the galaxy distribution down tob_II_ = 10^deg^. In this paper, we discuss the acquisition and reductionof the spectra, and we examine the qualitative features of the redshiftdistribution. The Great Wall and the Perseus-Pisces chain are not simplyconnected across the Zone of Avoidance. These structures, which at firstappear to be coherent on scales of ~100 h^-1^ Mpc or more, actually formthe boundaries of neighboring voids of considerably smaller scale,approximately 50h^-1^ Mpc. The structures delineated by ouroptically-selected sample are qualitatively similar to those detected bythe far-infrared-selected IRAS 1.2 Jansky Survey (Fisher et al. 1995).Although the IRAS survey probes more deeply into the Zone of Avoidance,our optically-selected survey provides better sampling of structures atb_II_ >= 10^deg^.
| 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.
| 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.
| Central Parts of Some Irregular Type-II Candidate Galaxies
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