We investigate the variation of current star formation in galaxies as a function of distance along three supercluster filaments , each joining pairs of rich clusters , in the Pisces-Cetus supercluster , which is part of the two-degree Field Galaxy Redshift Survey ( 2dFGRS ) .
We find that even though there is a steady decline in the rate of star formation , as well as in the fraction of star forming galaxies , as one approaches the core of a cluster at an extremity of such a filament , there is an increased activity of star formation in a narrow distance range between 3-4 h _ { 70 } ^ { -1 } Mpc , which is 1.5–2 times the virial radius of the clusters involved .
This peak in star formation is seen to be entirely due to the dwarf galaxies ( -20 < M _ { B } \leq -17.5 ) .
The position of the peak does not seem to depend on the velocity dispersion of the nearest cluster , undermining the importance of the gravitational effect of the clusters involved .
We find that this enhancement in star formation occurs at the same place for galaxies which belong to groups within these filaments , while group members elsewhere in the 2dFGRS do not show this effect .
We conclude that the most likely mechanism for this enhanced star formation is galaxy-galaxy harassment , in the crowded infall region of rich clusters at the extremities of filaments , which induces a burst of star formation in galaxies , before they have been stripped of their gas in the denser cores of clusters .
The effects of strangulation in the cores of clusters , as well as excess star formation in the infall regions along the filaments , are more pronounced in dwarfs since they more vulnerable to the effects of strangulation and harassment than giant galaxies .