Compare different parametric star formation history models

Example comparing different parametric star formation histories.

/home/runner/work/synthesizer/synthesizer/src/synthesizer/parametric/sf_hist.py:687: RuntimeWarning: divide by zero encountered in scalar power
  term1 = (age / self.peak_age) ** self.alpha

import matplotlib.pyplot as plt
import numpy as np
from unyt import Myr

from synthesizer.parametric.sf_hist import (
    Constant,
    DelayedExponential,
    DoublePowerLaw,
    Exponential,
    Gaussian,
    LogNormal,
)

models = [
    [Constant, {"max_age": 500 * Myr}],
    [Constant, {"max_age": 5000 * Myr, "min_age": 4000 * Myr}],
    [Gaussian, {"peak_age": 2000 * Myr, "sigma": 500 * Myr}],
    [Exponential, {"tau": -1000 * Myr, "max_age": 10000 * Myr}],
    [Exponential, {"tau": 10000 * Myr, "max_age": 10000 * Myr}],
    [DelayedExponential, {"tau": 1000 * Myr, "max_age": 8000 * Myr}],
    [LogNormal, {"tau": 0.5, "peak_age": 4000 * Myr, "max_age": 8000 * Myr}],
    [
        DoublePowerLaw,
        {
            "alpha": -2,
            "beta": 2.0,
            "peak_age": 3000 * Myr,
            "max_age": 8000 * Myr,
        },
    ],
]


for model, p in models:
    # initialise SFH model
    sfh = model(**p)

    # get star formation history
    age, sfr = sfh.calculate_sfh()

    # normalise to the peak
    sfr = sfr / np.max(sfr)

    # express the parameters as a string for use in a label
    parameter_str = " ".join([f"{k}={v}" for k, v in p.items()])

    # make label
    label = rf"{model.__name__} " + parameter_str

    plt.plot(age, sfr, label=label)

plt.ylim([0, 2])
plt.xlabel("age/Myr")
plt.ylabel("SFR/(Msun/yr)")
plt.legend(loc="upper left", fontsize=6)
plt.show()