The Discovery of a Proto-Spiral Galaxy
We are in the midst of a survey designed to detect and measure extremely low surface brightness galaxies (LSB’s); the most advanced of these surveys concerns the Virgo cluster. The galaxies of interest to us have a central (B) surface brightness of ≃ 25 mag aresec−2 or less and a typical sample is illustrated in Fig. 1. Most of these galaxies are devoid of nuclei so optical spectroscopy is not possible. Almost all of them are also devoid of gas, so we cannot establish their redshift. However the distribution of the galaxies is centred on the Virgo cluster, so on the basis of their low surface brightness and large angular size we identify them as cluster members (See Bingelli et al. 1987). Candidates are located on extremely deep photographs obtained by combining the information from photographically amplified (Malin 1978) derivatives of three sky-limited IIIaJ plates taken on the UK Schmidt telescope.
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