HII regions slides

For a typical O-star (e.g. the O6V star in the Trapezium)S = 10 49 s -1Typical nebula, n = 10 8 m -3 ; T e = 10 4 KAt r = 1 pc, J = 8.410 14 m 2 s -1giving X = 0.9999999i.e. the HII region is almost fully ionised!We can calculate this for a range of r-values X as a function of r