We present the Shapley Optical Survey , a photometric study covering a \sim 2 deg ^ { 2 } region of the Shapley Supercluster core at z \sim 0.05 in two bands ( B and R ) .
The galaxy sample is complete to B = 22.5 ( > M ^ { * } +6 , \mathrm { N _ { gal } } = 16 588 ) , and R = 22.0 ( > M ^ { * } +7 , \mathrm { N _ { gal } } = 28 008 ) .
The galaxy luminosity function can not be described by a single Schechter function due to dips apparent at B \sim 17.5 ( M _ { \mathrm { B } } \sim - 19.3 ) and R \sim 17.0 ( M _ { \mathrm { R } } \sim - 19.8 ) and the clear upturn in the counts for galaxies fainter than B and R \sim 18 mag .
We find , instead , that the sum of a Gaussian and a Schechter function , for bright and faint galaxies respectively , is a suitable representation of the data .
We study the effects of the environment on the photometric properties of galaxies , deriving the galaxy luminosity functions in three regions selected according to the local galaxy density , and find a marked luminosity segregation , in the sense that the LF faint-end is different at more than 3 \sigma confidence level in regions with different densities .
In addition , the luminosity functions of red and blue galaxy populations show very different behaviours : while red sequence counts are very similar to those obtained for the global galaxy population , the blue galaxy luminosity functions are well described by a single Schechter function and do not vary with the density .
Such large environmentally-dependent deviations from a single Schechter function are difficult to produce solely within galaxy merging or suffocation scenarios .
Instead the data support the idea that mechanisms related to the cluster environment , such as galaxy harassment or ram-pressure stripping , shape the galaxy LFs by terminating star-formation and producing mass loss in galaxies at \sim { \mathrm { M } } ^ { * } +2 , a magnitude range where blue late-type spirals used to dominate cluster populations , but are now absent .