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Date and Time of the Query: 2019-04-18 T09:31:32 PDT
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For refcode 1991A&A...252...27B:
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Copyright by European Southern Observatory (ESO). Reproduced by permission
1991A&A...252...27B Dwarf galaxies in the Virgo cluster I. The systematic photometric properties of early-type dwarfs B. Binggeli and L.M. Cameron Astronomisches Institut der Universitat Basel, Venusstrasse 7, CH-4102 Binningen, Switzerland Received September 7, 1990; accepted June 4, 1991 Abstract. We present the first results of an extensive photographic surface photometry of dwarf galaxies in the Virgo cluster. The mean radial surface brightness (SB) profiles of 174dE, 20 dS0, 24E & S0 and 7Sa galaxies are surveyed morphologically and analyzed by fitting model profiles. The main relationships found, and their interpretation, are as follows: 1. Faint dwarfs are very well described by an exponential or a King model profile. Brightward of M_B_~ - 16, the observed profiles are increasingly brighter in the central 1 to 3 kpc than either model fit predicts. These extended SB excesses should not be confused with the nuclei; nor with E-like bulges. 2. The magnitudes of the nuclei vary greatly at a given galaxian magnitude, but the maximum nuclear luminosity is a strong function of MT. The luminosity function of the nuclei is consistent with that of the globular clusters of M 87. 3. In the radius range 0.1 to 1 kpc, the logarithmically plotted profiles of all early-type galaxies come in two well-distinct classes which we identify with classical types versus dwarf types. The former are all classified E or S0. The latter comprise all galaxies classified dE or dSO; all morphologically "intermediate" types (d: E), and even two (mis-) classified "E"s. There are no true intermediate types between E and dE. The classical-dwarf dichotomy appears strongest in the King core parameter diagrams, but it is basically model-independent. There conditions for early mass loss by galactic winds must have been very critical. The bright dwarfs may have built up their bulge-like SB excess by secondary (late) star formation. 4. The mean SB profiles of dSO galaxies are indistinguishable from bright dE profiles. Two-dimensionally, the dS0s appear highly flattened and/or show asymmetric & irregular features, which may indicate their disk nature. Several arguments suggest that many (if not most) bright dwarfs may be rotationally supported disk galaxies, while most faint dwarfs may be spheroidals (supported by random motions). The transition at M_B_~-16 may reflect a critical mass for the formation or stability of stellar disks. Key words: galaxies: structure of - galaxies: dwarf elliptical - galaxies: elliptical
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