function inv_sig_crit, zq

;Purpose: to determine the inverse sigma crit as a function of redshift

;Input: redshift

;Output: inv_sig_crit(z)

;This program is a function that provides the inv_sig_crit at a
;certain redshift.  

;Calling Sequence: print,inv_sig_crit(z)
  ;must specify z as a variable or a single value

;To Plot: make z an array 
  ;plot,z,inv_sig_crit(z)

n=n_elements(zq)

num=100
z=findgen(num)/(num-1)+0.001
P=rho_gal(z,/dif)

sci_mean=fltarr(n)

for i=0L, n-1 do begin
    zi=zq[i]
    sci=sigcritinv_w(z,zi)
    totP=total(P)
    sci_mean[i]=total(P*sci)/totP
endfor

return,sci_mean
end