Fitting multiple Gaussians over quadratic bkgd

I have a histogram where I’d like to fit multiple Gaussians over a quadratic background, and draw it over the existing histogram. I have 8 Gaussian, each of which I want to constrain both the centroid and the FWHM (2nd and 3rd parameters), input manually in my script. Attached is the file containing the histogram.

hist.root (29.5 KB)

see example in attachment. To execute do

root > .x fitg.C+
fitg.C (1.37 KB)