0 Integrated intensity. (e.g. units I x km/s) 1 1st moment = sum(I*v)/sum(I) 2 dispersion = sqrt(sum(I*(v-M1)**2)/sum(I)) The v(i) are the axis values (e.g. velocities). M1 is the first moment. The moment is calculated independently for each pixel within the specified clip range. Default = 0. Note that mom=2 produces a map of sigma ('gaussian' dispersions), with FWHM = 2*sqrt(2*ln(2)) = 2.355 * sigma if the profile was a true gaussian.