def _add_ticks(xticks=True,yticks=True):
    """
    NAME:

       _add_ticks

    PURPOSE:

       add minor axis ticks to a plot

    INPUT:

       (none; works on the current axes)

    OUTPUT:

       (none; works on the current axes)

    HISTORY:

       2009-12-23 - Written - Bovy (NYU)

    """
    ax=pyplot.gca()
    if xticks:
        xstep= ax.xaxis.get_majorticklocs()
        xstep= xstep[1]-xstep[0]
        ax.xaxis.set_minor_locator(ticker.MultipleLocator(xstep/5.))
    if yticks:
        ystep= ax.yaxis.get_majorticklocs()
        ystep= ystep[1]-ystep[0]
        ax.yaxis.set_minor_locator(ticker.MultipleLocator(ystep/5.))