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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.
| Kinematics and dynamics of the MKW/AWM poor clusters
We report 472 new redshifts for 416 galaxies in the regions of the 23poor clusters of galaxies originally identified by Morgan, Kayser, andWhite (MKW), and Albert, White, and Morgan (AWM). Eighteen of the poorclusters now have 10 or more available redshifts within 1.5/h Mpc of thecentral galaxy; 11 clusters have at least 20 available redshifts. Basedon the 21 clusters for which we have sufficient velocity information,the median velocity scale is 336 km/s, a factor of 2 smaller than foundfor rich clusters. Several of the poor clusters exhibit complex velocitydistributions due to the presence of nearby clumps of galaxies. We checkon the velocity of the dominant galaxy in each poor cluster relative tothe remaining cluster members. Significantly high relative velocities ofthe dominant galaxy are found in only 4 of 21 poor clusters, 3 of whichwe suspect are due to contamination of the parent velocity distribution.Several statistical tests indicate that the D/cD galaxies are at thekinematic centers of the parent poor cluster velocity distributions.Mass-to-light ratios for 13 of the 15 poor clusters for which we havethe required data are in the range 50 less than or = M/LB(0)less than or = 200 solar mass/solar luminosity. The complex nature ofthe regions surrounding many of the poor clusters suggests that thesegroupings may represent an early epoch of cluster formation. Forexample, the poor clusters MKW7 and MKWS are shown to be gravitationallybound and likely to merge to form a richer cluster within the nextseveral Gyrs. Eight of the nine other poor clusters for which simpletwo-body dynamical models can be carried out are consistent with beingbound to other clumps in their vicinity. Additional complex systems withmore than two gravitationally bound clumps are observed among the poorclusters.
| Detection of H I in the elliptical galaxy NGC 5173
Westerbork Synthesis Radio Telescope observations of the ellipticalgalaxy NGC 5173 are described, and results on the H I distribution anddynamics of the galaxy are given. The mass of H I is 1.2 billion solarmasses and its mass-to-light ratio is 0.11 solar mass/solar luminosity.The galaxy shows strong 3727 A emission from its central regions whichsuggests a cause-and-effect relationship between the presence of the H Icloud and that of the H II region. The galaxy is not a source of radiocontinuum emission, however.
| On peculiar hot-spots nuclei of galaxies
Results are presented for spectrophotometry of the 'hot spot' nuclei ofthe peculiar galaxies NGC 613, 1365, 1404, 1433, 1672, 1792, 1808, and7552. The stellar content, reddening, and physical conditions in theemitting gas are examined. A major part of the continuous radiation isfound to be of stellar origin, and a model for the stellar component ofthe nuclear regions is developed. The computed properties of the nuclearregions are compared with observed characteristics of H II regions inother galaxies and of isolated extragalactic H II regions. A (U-B),(B-V) diagram for the eight galaxies is plotted, evolutionary tracks fora star-formation burst in a normal galaxy are superimposed on thediagram, and star formation in the nuclei is considered. It is concludedthat bursts of star formation have occurred in the central regions ofthese galaxies over the last 10 million years.
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