zheng07_model_dictionary¶
- halotools.empirical_models.zheng07_model_dictionary(threshold=-20, redshift=0.0, modulate_with_cenocc=False, **kwargs)[source]¶
Dictionary for an HOD-style based on Zheng et al. (2007), arXiv:0703457.
See Zheng et al. (2007) Composite Model for a tutorial on this model.
There are two populations, centrals and satellites. Central occupation statistics are given by a nearest integer distribution with first moment given by an
erf
function; the class governing this behavior isZheng07Cens
. Central galaxies are assumed to reside at the exact center of the host halo; the class governing this behavior isTrivialPhaseSpace
.Satellite occupation statistics are given by a Poisson distribution with first moment given by a power law that has been truncated at the low-mass end; the class governing this behavior is
Zheng07Sats
; satellites in this model follow an (unbiased) NFW profile, as governed by theNFWPhaseSpace
class.This composite model is built by the
HodModelFactory
.- Parameters:
- thresholdfloat, optional
Luminosity threshold of the galaxy sample being modeled. Default is set in the
model_defaults
module.- redshiftfloat, optional
Redshift of the galaxy population being modeled. If you will be using the model instance to populate mock catalogs, you must choose a redshift that is consistent with the halo catalog. Default is set in the
model_defaults
module.- modulate_with_cenoccbool, optional
If set to True, the
Zheng07Sats.mean_occupation
method will be multiplied by the the first moment of the centrals:\(\langle N_{\mathrm{sat}}\rangle_{M}\Rightarrow\langle N_{\mathrm{sat}}\rangle_{M}\times\langle N_{\mathrm{cen}}\rangle_{M}\)
The \(\langle N_{\mathrm{cen}}\rangle_{M}\) function is calculated according to
Zheng07Cens.mean_occupation
.
- Returns:
- model_dictionarydict
Dictionary of keywords to be passed to
HodModelFactory
Notes
Although the
cenocc_model
is a legitimate keyword for theZheng07Sats
class, this keyword is not permissible when building thezheng07
composite model with thePrebuiltHodModelFactory
. To build a composite model that uses this feature, you will need to use theHodModelFactory
directly. See Advanced usage of the zheng07 model for explicit instructions.Examples
>>> from halotools.empirical_models import PrebuiltHodModelFactory >>> model_instance = PrebuiltHodModelFactory('zheng07', threshold = -21)
As with all instances of the
PrebuiltHodModelFactory
, you can populate a mock by passing the model a halo catalog:>>> from halotools.sim_manager import FakeSim >>> halocat = FakeSim(redshift = model_instance.redshift) >>> model_instance.populate_mock(halocat)