r = (Sqrt[(x^2) + (y^2)])
N1s = (1/(Sqrt[8 π]))
ss = 
      N1s (E^(-(Sqrt[(x^2) + (y^2)]))) + 
        N1s (E^(-(Sqrt[(((x + 1))^2) + (((y - 5))^2)]))) + 
        N1s (E^(- 2 (Sqrt[(((x - 1))^2) + (((y - 3))^2)]))) + 
        N1s (E^(- 3 (Sqrt[(((x - 2))^2) + (((y - 1))^2)])))
ContourPlot[ss, {x, -5, 5}, {y, -5, 8}, 
      PlotPoints -> 200]
DensityPlot[ss, {x, -5, 5}, {y, -5, 8}, 
      PlotPoints -> 
        71]