def plotCastro(castroData, ylims, nstep=25, zlims=None):
    """ Make a color plot (castro plot) of the 
        delta log-likelihood as a function of 
        energy and flux normalization

    castroData : A CastroData object, with the 
                 log-likelihood v. normalization for each energy bin
    ylims      : y-axis limits
    nstep      : Number of y-axis steps to plot for each energy bin
    zlims      : z-axis limits

    returns fig,ax,im,ztmp which are matplotlib figure, axes and image objects
    """
    xlabel = "Energy [MeV]"
    ylabel = NORM_LABEL[castroData.norm_type]
    return plotCastro_base(castroData, ylims,
                           xlabel, ylabel, nstep, zlims)
Make a color plot (castro plot) of the 
        delta log-likelihood as a function of 
        energy and flux normalization

    castroData : A CastroData object, with the 
                 log-likelihood v. normalization for each energy bin
    ylims      : y-axis limits
    nstep      : Number of y-axis steps to plot for each energy bin
    zlims      : z-axis limits

    returns fig,ax,im,ztmp which are matplotlib figure, axes and image objects