def Lsynch_murphy(sfr, nu):
    """
    Synchrotron luminosity model, taken from Eq. 9 of Bonaldi et al. 
    (arXiv:1805.05222).
    
    Parameters
    ----------
    sfr : array_like
        Star-formation rate, in Msun/yr.
    
    nu : array_like
        Frequency, in GHz.
    
    Returns
    -------
    L_synch : array_like, float
        Synchrotron luminosity in W Hz^-1.
    """
    freq_fac = nu**(-0.85) / (1. + (nu / 20.)**0.5)
    return 1.9e21 * sfr * freq_fac