def garrisonkimmel(x):
    """Garrison-Kimmel 2014 Stellar-Halo-Mass function at redshift zero.
    MNRAS 438, 2578–2596 (2014)
    Equation 4

    Keyword arguments:
    x -- array of peak halo masses
    """
    tr = 3.0e6 * (x/1.0e10)**1.92
    return tr