ENH: galaxy-quenching model

docs/galaxies.rst

@@ -89,6 +89,10 @@ The following models are found in the `skypy.galaxies.stellar_mass` package.
   :nosignatures:
 
   schechter_smf_mass
+  schechter_smf_phi_centrals
+  schechter_smf_phi_satellites
+  schechter_smf_phi_mass_quenched
+  schechter_smf_phi_satellite_quenched
 
 
 Velocity dispersion

skypy/galaxies/stellar_mass.py

@@ -9,6 +9,10 @@
 
 __all__ = [
     'schechter_smf_mass',
+    'schechter_smf_phi_centrals',
+    'schechter_smf_phi_satellites',
+    'schechter_smf_phi_mass_quenched',
+    'schechter_smf_phi_satellite_quenched',
 ]
 
 
@@ -78,3 +82,132 @@ def schechter_smf_mass(redshift, alpha, m_star, m_min, m_max, size=None,
     m = schechter(alpha, x_min, x_max, resolution, size=size, scale=m_star)
 
     return m
+
+
+def schechter_smf_phi_centrals(phi_blue_total, fsatellite):
+    r'''Schechter amplitude of central galaxies.
+    This function returns the Schechter mass function amplitude
+    for active central population based on equation (15)
+    in de la Bella et al. 2021 [1]_.
+
+    Parameters
+    ----------
+    phi_blue_total: array_like
+        Schechter mass function amplitude for the entire active
+        sample of galaxies, :math:`(\phi_b, \alpha_b, m_{*})`.
+
+    fsatellite: array_like
+        Fraction of active satellite galaxies between 0 and 1.
+        It could be a float or an array, depending on the model you choose.
+
+    Returns
+    -------
+    amplitude: array_like
+        Amplitude of the Schechter mass function.
+
+     References
+    ----------
+    .. [1] de la Bella et al. 2021, Quenching and Galaxy Demographics,
+           arXiv 2112.11110.
+
+    '''
+
+    sum_phics = (1 - fsatellite) * (1 - np.log(1 - fsatellite))
+
+    return (1 - fsatellite) * phi_blue_total / sum_phics
+
+
+def schechter_smf_phi_satellites(phi_centrals, fsatellite):
+    r'''Schechter amplitude of satellite galaxies.
+    This function returns the Schechter mass function amplitude
+    for active satellite population based on equation (15)
+    in de la Bella et al. 2021 [1]_.
+
+    Parameters
+    ----------
+    phi_centrals: array_like
+        Schechter mass function amplitude of the central
+        active galaxies.
+
+    fsatellite: float, (nm, ) array_like
+        Fraction of active satellite galaxies between 0 and 1.
+        It could be a float or an array, depending on the model you choose.
+
+    Returns
+    -------
+    amplitude: array_like
+        Amplitude of the Schechter mass function.
+
+    References
+    ----------
+    .. [1] de la Bella et al. 2021, Quenching and Galaxy Demographics,
+           arXiv 2112.11110.
+
+    '''
+
+    return _satellite_computation(phi_centrals, fsatellite)
+
+
+def schechter_smf_phi_mass_quenched(phi_centrals, phi_satellites):
+    r'''Schechter amplitude of mass-quenched galaxies.
+    This function returns the Schechter mass function amplitude
+    for passive mass-quenched population based on equation (15)
+    in de la Bella et al. 2021 [1]_.
+
+    Parameters
+    ----------
+    phi_centrals: array_like
+        Schechter mass function amplitude of the central
+        active galaxies.
+
+    phi_satellites: array_like
+        Schechter mass function amplitude of the satellite
+        active galaxies.
+
+    Returns
+    -------
+    amplitude: array_like
+        Amplitude of the Schechter mass function.
+
+    References
+    ----------
+    .. [1] de la Bella et al. 2021, Quenching and Galaxy Demographics,
+           arXiv 2112.11110.
+
+    '''
+
+    return phi_centrals + phi_satellites
+
+
+def schechter_smf_phi_satellite_quenched(phi_satellites, fenvironment):
+    r'''Schechter amplitude of satellite-quenched galaxies.
+    This function returns the Schechter mass function amplitude
+    for active central population based on equation (15)
+    in de la Bella et al. 2021 [1]_.
+
+    Parameters
+    ----------
+    phi_satellites: array_like
+        Schechter mass function amplitude of the satellite
+        active galaxies.
+
+    fenvironment: float
+        Fraction of satellite-quenched galaxies between 0 and 1.
+
+    Returns
+    -------
+    amplitude: array_like
+        Amplitude of the Schechter mass function.
+
+    References
+    ----------
+    .. [1] de la Bella et al. 2021, Quenching and Galaxy Demographics,
+           arXiv 2112.11110.
+
+    '''
+
+    return _satellite_computation(phi_satellites, fenvironment)
+
+
+def _satellite_computation(amplitude, fraction):
+    return - np.log(1 - fraction) * amplitude

skypy/galaxies/tests/test_stellar_mass.py

@@ -3,6 +3,9 @@
 import scipy.integrate
 from scipy.special import gammaln
 import pytest
+
+from hypothesis import given
+from hypothesis.strategies import integers
 from astropy.modeling.models import Exponential1D
 
 from skypy.galaxies import stellar_mass
@@ -79,3 +82,81 @@ def calc_cdf(m):
                                              size=1000, resolution=100)
     p_value = scipy.stats.kstest(sample, calc_cdf)[1]
     assert p_value >= 0.01
+
+
+def test_schechter_smf_phi_centrals():
+    # Scalar inputs
+    phiblue_scalar = 10**-2.423
+    fsat_scalar = 0.4
+
+    # Array inputs
+    phiblue_array = np.array([10**-2.423, 10**-2.422])
+    fsat_array = np.array([0.40, 0.41, 0.42])
+
+    # Test for scalar output
+    phic_scalar = stellar_mass.schechter_smf_phi_centrals(phiblue_scalar, fsat_scalar)
+    assert np.isscalar(phic_scalar)
+
+    # Test for 1 dim output
+    phic_1d_phib = stellar_mass.schechter_smf_phi_centrals(phiblue_array, fsat_scalar)
+    phic_1d_fsat = stellar_mass.schechter_smf_phi_centrals(phiblue_scalar, fsat_array)
+    assert phic_1d_phib.shape == phiblue_array.shape
+    assert phic_1d_fsat.shape == fsat_array.shape
+
+    # Test for 2 dim output
+    phic_2d = stellar_mass.schechter_smf_phi_centrals(phiblue_array[:, np.newaxis], fsat_array)
+    assert phic_2d.shape == (len(phiblue_array), len(fsat_array))
+
+    # Special case
+    fsat_special = 1 - np.exp(-1)
+    phic_special = stellar_mass.schechter_smf_phi_centrals(phiblue_scalar, fsat_special)
+    assert phic_special == 0.5 * phiblue_scalar
+
+
+@given(integers(), integers())
+def test_schechter_smf_phi_mass_quenched(phic, phis):
+
+    # Array inputs
+    phic_1d = np.array([phic, phic])
+    phis_1d = np.array([phis, phis])
+
+    # Test for scalar output
+    phimq_scalar = stellar_mass.schechter_smf_phi_mass_quenched(phic, phis)
+    assert np.isscalar(phimq_scalar)
+    assert phimq_scalar == phic + phis
+
+    # Test for array output
+    phimq_1d = stellar_mass.schechter_smf_phi_mass_quenched(phic_1d, phis_1d)
+    assert phimq_1d.shape == phic_1d.shape == phis_1d.shape
+    assert np.all(phimq_1d == phic_1d + phis_1d)
+
+
+SATELLITE_FUNCTIONS = [
+    stellar_mass.schechter_smf_phi_satellites,
+    stellar_mass.schechter_smf_phi_satellite_quenched,
+]
+
+
+@pytest.mark.parametrize('satellite_function', SATELLITE_FUNCTIONS)
+def test_schechter_smf_phi_satellites_common(satellite_function):
+    # Scalar inputs
+    phis_scalar = 10**-2.423
+    fraction_scalar = 0.2
+
+    # Array inputs
+    phis_array = np.array([10**-2.423, 10**-2.422])
+
+    # Test for scalar output
+    phis_sat_scalar = satellite_function(phis_scalar, fraction_scalar)
+    assert np.isscalar(phis_sat_scalar)
+
+    # Test for 1 dim output
+    phis_sat_1d_phib = satellite_function(phis_array, fraction_scalar)
+    assert phis_sat_1d_phib.shape == phis_array.shape
+
+    # Corner case no satellite galaxies
+    fraction_null = 0
+    phis_sat_null_scalar = satellite_function(phis_scalar, fraction_null)
+    phis_sat_null_array = satellite_function(phis_array, fraction_null)
+    assert phis_sat_null_scalar == 0
+    assert np.all(phis_sat_null_array == np.zeros(len(phis_array)))