M 32 is a galaxy with very unusual characteristics. Compared to dwarf galaxies having similar absolute brightness () its central surface brightness () is 4 orders of magnitudes higher and its core radius () 3 orders of magnitude smaller (Kormendy, 1985). Within the two planes ` ' and ` ', M 32 lies approximately on the extension of the sequence defined by elliptical galaxies and is clearly distinct from the low surface brightness dwarf galaxies following a different sequence (cf. with Fig. 1). Therefore, M 32 is often denoted as a dwarf elliptical galaxy and the other dwarf galaxies as dwarf spheroidals (dSph) (Kormendy, 1987; Djorgovski, 1992), whereas other authors use the term compact elliptical for M 32 and dwarf elliptical for the low surface brightness objects only (Sandage and Binggeli, 1984; Bender et al., 1993)). So far, only very few other galaxies with properties similar to M 32 have been found (Sandage and Binggeli, 1984; Nieto and Prugniel, 1987; Davidge, 1991; Kormendy and Bender, 1994). But none of these galaxies has such extreme properties as M 32.
Ferguson & Sandage (1990) classified a number of galaxies in nearby groups as possible M 32-type objects due to their compact appearance on photographic plates (similar to NGC 4486B in Sandage & Binggeli (1984) though NGC 4486B is still 2 mag brighter than M 32). We obtained spectroscopy of these candidate galaxies in the Leo group during a longer observing run within our project to study the evolution of elliptical galaxies (Bender et al., 1996; Ziegler and Bender, 1997). The galaxies were drawn from Table II of Ferguson & Sandage (1990) and are designated in the following as Leo # , where # corresponds to the number assigned in that table.
In the following sections we briefly describe the observations and their analysis, present the results and draw our conclusions.
© European Southern Observatory (ESO) 1998
Online publication: January 27, 1998