Galaxy morphologies and environment in the Abell 901/902 supercluster from COMBO-17

ABSTRACT We present a morphological study of galaxies in the A901/902 supercluster from theCOMBO-17 survey. A total of 570 galaxies with photometric redshifts in the range 0:155 1:5 a classical morphology-density relation isfound. A correlation is also found between morphology and local projected surface mass den-sity, but no trend is observed with distance to the nearest cluster. This supports the finding thatlocal environment is more important to galaxy morphology than global cluster properties. Thebreakdown of the morphological catalogue by colour shows a dominance of blue galaxies inthe galaxies displaying late-type morphologies and a corresponding dominance of red galax-ies in the early-type population. Using the 17-band photometry from COMBO-17, we furthersplit the supercluster red sequence into old passive galaxies and galaxies with young stars anddust according to the prescription of Wolf et al. (2005). We find that the dusty star-formingpopulation describes an intermediate morphological group between late-type and early-typegalaxies, supporting the hypothesis that field and group spiral galaxies are transformed intoS0s and, perhaps, ellipticals during cluster infall.Key words: galaxies: clusters: general — galaxies: evolution — galaxies: interactions