AIMS: We analyse the photometric properties of the early-type Fornax cluster
dwarf galaxy population, based on a wide field imaging study of the central
cluster area in V and I. We used the instrument/telescope combination
IMACS/Magellan at Las Campanas Observatory, providing much larger light
collecting area and better image resolution than previous surveys.
METHODS: We create a fiducial sample of Fornax cluster dwarf ellipticals
(dEs) in the following three steps: (1) To verify cluster membership, we
measured I-band surface brightness fluctuation (SBF) distances to candidate
dEs; (2) We re-assessed morphological classifications for candidate dEs too
faint for SBF detection; and (3) We searched for new candidate dEs in the
size-luminosity regime close to the resolution limit of previous surveys.
RESULTS: (1) We confirm cluster membership for 28 candidate dEs in the range
-16.6<M_V<-10.1 mag by means of SBF distances. We find no SBF background
galaxy. (2) Of 51 further candidate dEs in the range -13.2<M_V<-8.6 mag, 2/3
are confirmed as probable cluster members by morphological re-assessment, while
1/3 are re-classified as probable background objects. (3) We find 12 new dE
candidates in the range -12.3<M_V<-8.8 mag.
The surface brightness-magnitude relation defined by the resulting fiducial
dE sample shows that Fornax dEs are about 40% larger than Local Group dEs. The
Fornax dE sample furthermore defines a colour-magnitude relation that appears
slightly shallower than that of Local Group dEs. The early-type dwarf galaxy
luminosity function in Fornax has a faint end slope alpha = -1.1 +/- 0.1.
We discuss these findings in the context of structure formation theories.
(ABRIDGED)Comment: 15 pages, 10 figures, accepted for publication in A&A. Uses special
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