The relationship of high surface brightness Arakelian galaxies (ArG) to their environment is studied. This is done using the groups identified by the authors on the basis of the CfA2 red shift survey. Of the 15577 galaxies in the sample, 172 (1.104%) have a high surface brightness. The corresponding percentage for the galaxies with 0 . 15 0 . 13 ≤ < m is 2.05. The following results are obtained: (a) On going from single to poor groups and on to more populated groups, the frequency of occurrence of ArG does not vary. (b) Groups of galaxies containing ArG do not differ on the average from groups which do not contain such galaxies in terms of their dynamic characteristics, such as the dispersion in radial velocity, size, and total luminosity, or their morphological content. (c) ArG do not follow the regular pattern according to whichelliptical and lenticular galaxies are more often encountered in groups of galaxies than among single galaxies, i.e., it seems that the frequency of occurrence of elliptical and lenticular ArG in groups is the same as in single galaxies. (d) The surface brightnesses, diameters, and luminosities of ArG in groups of galaxies are greater than those of single ArG. This shows up especially strongly in spiral ArG.
The morphological content of Markarian galaxies (MG) in groups and in single galaxies is examined. It is found that MG do not conform to the long established rule that the relative number of elliptical and lenticular galaxies in groups is higher than in single galaxies.The relationship of high surface brightness Arakelian galaxies to their environment was studied in Ref. 1. In particular, it was found that these galaxies do not conform to the well established rule according to which elliptical and lenticular galaxies are encountered more often in groups of galaxies than among single galaxies. In this note we obtain analogous statistics for Markarian galaxies with an ultraviolet continuum.We use the same sample [2] as in Ref. 1 for the list of groups of galaxies.Here we discuss the morphological distribution of Markarian galaxies which are members of groups and those which are single. Since the number of Markarian galaxies of known morphological types in the CfA2 catalog is small, we divide the galaxies into two parts with respect to their morphological type: elliptical (elliptical and lenticular) and spiral.In order to reduce the effect on the results owing to differences in the distributions of the visible stellar magnitudes, as well to differences in the mean distances of the samples, we impose limits on the stellar magnitudes (m = 13-15) and radial velocities (V = 2000-8000 km/s) of the samples of galaxies to be compared.
The characteristics of galaxies within galaxy groups are investigated as a function of the surroundings. It is shown that the relative number of the galaxies with different morphological type is correlated with the pumber of members within the group, but the fraction of E+SO galaxies does not depend on the mean-pairwise distance between the galaxies, the density of the luminous matter as well as the velocity dispersion in the group.Key words: galaxies -morphology AAA subject claaaification: 159 IntroductionIt is a well known phenomenon, that along the sequence "regular galaxy cluster -irregular galaxy cluster -field galaxies" the relative number of elliptical and lenticular galaxies decreases. This is equivalent to the finding that the relative number of spiral galaxies increases with a decreasing galaxy concentration in the central parts of the clusters (Butcher and Oemler Jr. 1978, White 1978. Moreover, the morphological composition of clusters clearly changes within its borders. Melnik and Sargent (1977) found an increase of the number density of spiral galaxies compared to ellipticals with growing distance from the center of rich clusters which are X-ray emitters. Later on this phenomenon was found in many other g a l w clusters (Huchra et al. 1984, Lucey et al. 1986, Schneider et al. 1986, Binggeli et al. 1987). According to Dressler (1980) the morphological composition of a cluster is determined to a greater degree by the local galaxy density than the total density of the cluster. This correlation was confirmed by Giovanelli et al. (1986) and Quintana et al. (1985), too.There are many ideas to explain the observed distribution of galaxies (see the reviews of Arakelian 1981, Gorbatski and Kritsuk 1987, Sarazin 1986).They can be divided in two groups. The first one of them argues that the property and the type of the galaxies depend on primordial conditions in the epoch of galaxy formation, and after this the changes were negligible. The other group suggests, that the galaxy were formed everywhere with the same morphological distribution, but then physical processes which depend on the surrounding medium changed the morphological type of the galaxies.But regardless of the arguments of the opponents of the two groups a crucial question remains till now: In which epoch of the galaxy evolution their morphological type is taken shape and by what it is stipulated?Compared to galaxy clusters the investigations of poor clusters or groups of galaxies do not show very clearly the existence and essence of the correlation between the characteristics of the galaxies and the one of galaxy systems.Mahtessian (1982,1983,1985, 1989) investigated the characteristics of the galaxies depending on the surroundings and the morphological content of the group using a sample of galaxy groups of Karachentsev (1970). It was found that the characteristic parameters of the galaxies are stronger correlated with the morphological composition of the group than with its density. In particular the population fraction of subclasses and ...
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