def strolger_15(z, **kwargs):
    """
    star formation history
    https://arxiv.org/pdf/1509.06574.pdf

    result is in solar masses/year/Mpc^3

    Can match Figure 6, if the h^3 factor is divided out
    """
    rate = (1+z)**5.0 / (1 + ((1+z)/1.5)**6.1)

    return rate