Star Formation Rate and Environment in the SDSS-DR4

We investigate the environmental dependence of galaxies with the star formation rate (SFR) in a complete volume limited sample of 91566 galaxies, in the redshift range $0.05 \le z \le 0.095$, and with $M_r=-20.0$ (that is M$^*$ + 1.45), selected from the Sloan Digital Sky Survey Data Release 4 (SDSS-DR4). The environment is characterized by the local number density of galaxies, defined by the parameter $\Sigma_{N}(\frac{N}{\pi*r_{N}^{2}})$, with N=5. We find a reletaion between the distance of the nearest neighbour and the SFR, and confirm the general trend for the SFR of decreasesing with increasing density.