def compute_sigmag(Sigma_sfr, k, ks_fit=1.4):
    """
    Gas surface density from the SFR surface density assuming modified Kennicutt-Schmidt relation. 
    Sigma_sfr in Msun/yr/kpc^2
    k is the burstiness parameter
    """
    out=(((k*(10.0**-12))**-1)*Sigma_sfr)**(1./ks_fit)
    return out