def freq_in_kmskpc(vo,ro):
    """
    NAME:

       freq_in_kmskpc

    PURPOSE:

       convert a frequency to km/s/kpc

    INPUT:

       vo - velocity unit in km/s

       ro - length unit in kpc

    OUTPUT:

       conversion from units where vo=1. at ro=1.

    HISTORY:

       2013-09-01 - Written - Bovy (IAS)

    """
    return vo/ro