A comprehensive study of 12 very rich clusters of galaxies. I - Photometric technique and analysis of the luminosity function

Abstract

view Abstract Citations (174) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A comprehensive study of 12 very rich clusters of galaxies. I. Photometric technique and analysis of the luminosity function. Dressler, A. Abstract A study of 12 very rich clusters of galaxies based on photographic photometry has been completed at Lick Observatory. A detailed analysis of the luminosity functions indicates that, although they are similar in general appearance, variations exist which are significantly greater than would be expected for statistical fluctuations of a universal function. The differences are discussed in terms of variation of the Schechter parameters M*, the bright-end turnover, and a, the faint-end slope. Two clusters have deviations from "M*nniversai" in the 3-4 a range, A274 showing an excess and A2029 a deficiency of bright galaxies for their respective richnesses. Some attention is also given to evidence for different forms of the luminosity function, as may be exemplified by Al68. The nonuniversality of the luminosity function implies that M* may be unreliable as a standard candle. It is unclear from available data, however, whether the fluctuations in M* are correlated with cluster characteristics in such a way that the distance of a cluster could systematically affect estimation of its distance modulus. Thus the usefulness of M* as a standard candle is questionable until the nature and extent of variations in this parameter are better understood. The use of the first-ranked cluster member as a standard candle is also investigated. Clusters such as A2029 indicate that the first-ranked cluster member is a special object in at least some cases, lending some support to its use as a standard candle. The small scatter in M, for these 12 clusters can be reduced even further if a correction for Bautz-Morgan Type is applied. The rms variation in M, after correction is only + 0.33 mag. The unusually steep bright ends of luminosity functions for clusters containing cD galaxies, as in A2029, suggest that cannibalism of massive cluster members by the cD galaxy could be responsible for evolutionary changes in the distribution. On the other hand, A665 also has a steep bright end, but has no cD galaxy. This example, together with A274 where the number of bright galaxies significantly exceeds that predicted by the universal distribution, indicates that there are cases where the differences in the distributions are more likely to be initial ones than evolutionary ones. Subject headings: galaxies: clusters of - galaxies: photometry - luminosity function Publication: The Astrophysical Journal Pub Date: August 1978 DOI: 10.1086/156310 Bibcode: 1978ApJ...223..765D Keywords: Astronomical Photography; Astronomical Photometry; Galactic Clusters; Luminous Intensity; Astronomical Models; Cosmology; Galactic Radiation; Spatial Distribution; Standard Deviation; Statistical Analysis; Astronomy; Clusters of Galaxies:Luminosity Function; Clusters of Galaxies:Photometry full text sources ADS | data products SIMBAD (12) Related Materials (2) Part 2: 1978ApJ...226...55D Part 3: 1978LicOB.771....1D