HeavisideAssembias

class halotools.empirical_models.HeavisideAssembias(**kwargs)

Bases: object

Class used as an orthogonal mix-in to introduce step function-style assembly-biased behavior into any component model.

No positional arguments accepted; all argument are strictly keyword arguments.

Parameters:

method_name_to_decoratestring

Name of the method in the primary class whose behavior is being decorated

lower_assembias_boundfloat

lower bound on the method being decorated with assembly bias

upper_assembias_boundfloat

upper bound on the method being decorated with assembly bias

sec_haloprop_keystring, optional

String giving the column name of the secondary halo property governing the assembly bias. Must be a key in the table passed to the methods of HeavisideAssembiasComponent. Default value is specified in the model_defaults module.

splitfloat or list, optional

Fraction or list of fractions between 0 and 1 defining how we split halos into two groupings based on their conditional secondary percentiles. Default is 0.5 for a constant 50/50 split.

split_abscissalist, optional

Values of the primary halo property at which the halos are split as described above in the split argument. If loginterp is set to True (the default behavior), the interpolation will be done in the logarithm of the primary halo property. Default is to assume a constant 50/50 split.

splitting_modelobject, optional

Model instance with a method called splitting_method_name used to split the input halos into two types.

splitting_method_namestring, optional

Name of method bound to splitting_model used to split the input halos into two types.

halo_type_tupletuple, optional

Tuple providing the information about how elements of the input table have been pre-divided into types. The first tuple entry must be a string giving the column name of the input table that provides the halo-typing. The second entry gives the value that will be stored in this column for halos that are above the percentile split, the third entry gives the value for halos below the split.

If provided, you must ensure that the splitting of the table was self-consistently performed with the input split, or split_abscissa and split_ordinates, or split_func keyword arguments.

assembias_strengthfloat or list, optional

Fraction or sequence of fractions between -1 and 1 defining the assembly bias correlation strength. Default is 0.5.

assembias_strength_abscissalist, optional

Values of the primary halo property at which the assembly bias strength is specified. Default is to assume a constant strength of 0.5. If passing a list, the strength will interpreted at the input assembias_strength_abscissa. Default is to assume a constant strength of 0.5.

loginterpbool, optional

If set to True, the interpolation will be done in the logarithm of the primary halo property, rather than linearly. Default is True.

Methods Summary

assembias_decorator(func)	Primary behavior of the HeavisideAssembias class.
assembias_strength(prim_haloprop)	Method returns the strength of assembly bias as a function of the primary halo property.
percentile_splitting_function(prim_haloprop)	Method returns the fraction of halos that are type-2 as a function of the input primary halo property.

Methods Documentation

assembias_decorator(func)

Primary behavior of the HeavisideAssembias class.

This method is used to introduce a boost/decrement of the baseline function in a manner that preserves the all-halo result. Any function with a semi-bounded range can be decorated with assembias_decorator. The baseline behavior can be anything whatsoever, such as mean star formation rate or mean halo occupation, provided it has a semi-bounded range.

Parameters:

funcfunction object

Baseline function whose behavior is being decorated with assembly bias.

Returns:

wrapperfunction object

Decorated function that includes assembly bias effects.

assembias_strength(prim_haloprop)

Method returns the strength of assembly bias as a function of the primary halo property.

Parameters:

prim_haloproparray_like

Array storing the primary halo property.

Returns:

strengtharray_like

Strength of assembly bias as a function of the input halo property.

percentile_splitting_function(prim_haloprop)

Method returns the fraction of halos that are type-2 as a function of the input primary halo property.

Parameters:

prim_haloproparray_like

Array storing the primary halo property.

Returns:

splitfloat

Fraction of type2 halos at the input primary halo property.