vdB03Quiescence

class halotools.hod_components.vdB03Quiescence(gal_type, parameter_dict={'quiescence_abcissa': [12, 15], 'quiescence_ordinates': [0.25, 0.75]}, interpol_method='spline', input_spline_degree=3)

Bases: object

Traditional HOD-style model of galaxy quenching in which the expectation value for a binary SFR designation of the galaxy is purely determined by the primary halo property.

Approach is adapted from van den Bosch et al. 2003. The parameters of this component model govern the value of the quiescent fraction at a particular set of masses. The class then uses an input halotools.occupation_helpers function to infer the quiescent fraction at values other than the input abcissa.

Notes

In the construction sequence of a composite HOD model, if halotools.hod_designer uses this component model after using a central occupation component, then the resulting central galaxy stellar-to-halo mass relation will have no dependence on quenched/active designation. Employing this component before the occupation component allows for an explicit halo mass dependence in the central galaxy SMHM. Thus the sequence of the composition of the quiescence and occupation models determines whether the resulting composite model satisfies the following classical separability condition between stellar mass and star formation rate:

Parameters:

gal_type : string, optional

Sets the key value used by halotools.hod_designer and hod_factory to access the behavior of the methods of this class.

parameter_dict : dictionary, optional

Dictionary specifying what the quiescent fraction should be at a set of input values of the primary halo property. Default values are set in halotools.defaults.

interpol_method : string, optional

Keyword specifying how mean_quiescence_fraction evaluates input value of the primary halo property that differ from the small number of values in self.parameter_dict. The default spline option interpolates the model’s abcissa and ordinates. The polynomial option uses the unique, degree N polynomial passing through the ordinates, where N is the number of supplied ordinates.

input_spline_degree : int, optional

Degree of the spline interpolation for the case of interpol_method=’spline’. If there are k abcissa values specifying the model, input_spline_degree is ensured to never exceed k-1, nor exceed 5.

Methods Summary

mean_quiescence_fraction(input_abcissa)

Expected fraction of gal_type galaxies that are quiescent as a function of the primary halo property.

Methods Documentation

mean_quiescence_fraction(input_abcissa)

Expected fraction of gal_type galaxies that are quiescent as a function of the primary halo property.

Parameters:

input_abcissa : array_like

array of primary halo property at which the quiescent fraction is being computed.

Returns:

mean_quiescence_fraction : array_like

Values of the quiescent fraction evaluated at input_abcissa.

Notes

Either assumes the quiescent fraction is a polynomial function of the primary halo property, or is interpolated from a grid. Either way, the behavior of this method is fully determined by its values at the model abcissa, as specified in parameter_dict.