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Photometric investigations of compact galaxies
Author(s) -
Börngen F.,
Kalloghlian A. T.
Publication year - 1985
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.2113060209
Subject(s) - physics , astrophysics , galaxy , halo , stars
No exact definition of compact galaxes with regard to their degree of concentration exists up to now. 169 objects visually selected by Z WICKY respectively B ÖRNGEN and K ALLOGHLIAN in the field ZwCl 1710.4 + 6401 are analysed photometrically and morphologically. The brighness profiles are determined by means of equidensities calibrated into intensities. The different parts of these profiles are investigated with regard to their utility of an objective description of compact galaxies. Whereas the halo is not suitable, a classification is practicable by means of the gradient G of the middle part of the profile. Especially, it is shown that the (lg I max , m )‐diagram is well suited to represent the compact galaxies. In an interval of some magnitudes in which the density of star images is not yet saturated the positions of stars and compact galaxies differ significantly. The star positions obey a linear relation which is used for the calibration of our method and for the derivation of the plate constants. By means of the characteristic quantity m 0 and the compactness k one gets a quantitative characterization of compact galaxies and a subdivision into the classes K = 1, 2, and 3. Extreme compact galaxies ( K = o) are difficult or not at all discernible from stars, galaxies of the class K = 4 are no more compact.