Kravtsov04Sats

class halotools.hod_components.Kravtsov04Sats(parameter_dict=None, threshold=-20, gal_type='satellites', central_occupation_model=None)

Bases: object

Power law model for the occupation statistics of satellite galaxies, introduced in Kravtsov et al. 2004, arXiv:0308519.

Parameters:

parameter_dict : dictionary, optional.

Contains values for the parameters specifying the model. Dictionary keys are ‘logMmin_cen’ and ‘sigma_logM’

Their best-fit parameter values provided in Table 1 of Zheng et al. (2007) are pre-loaded into this class, and can be accessed via the published_parameters method.

threshold : float, optional.

Luminosity threshold of the mock galaxy sample. If specified, input value must agree with one of the thresholds used in Zheng07 to fit HODs: [-18, -18.5, -19, -19.5, -20, -20.5, -21, -21.5, -22]. Default value is specified in the defaults module.

gal_type : string, optional

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

central_occupation_model : occupation model instance, optional

If present, the mean occupation method of this model will be multiplied by the value of central_occupation_model at each mass, as in Zheng et al. 2007. Default is None.

Methods Summary

mc_occupation(logM)	Method to generate Monte Carlo realizations of the abundance of galaxies.
mean_occupation(logM)	Expected number of satellite galaxies in a halo of mass logM.
published_parameters(threshold)	Best-fit HOD parameters from Table 1 of Zheng et al.

Methods Documentation

mc_occupation(logM)

Method to generate Monte Carlo realizations of the abundance of galaxies. Assumes gal_type galaxies obey Poisson statistics.

Parameters:

logM : array

array of of halos in catalog

Returns:

mc_abundance : array

array of length len(logM) giving the number of self.gal_type galaxies in the halos.

mean_occupation(logM)

Expected number of satellite galaxies in a halo of mass logM. See Equation 5 of arXiv:0703457.

Parameters:

logM : array

array of of halos in catalog

halo_type : array

array of halo types. Entirely ignored in this model. Included as a passed variable purely for consistency between the way this function is called by different models.

Returns:

mean_nsat : float or array

Mean number of satellite galaxies in a host halo of the specified mass.

published_parameters(threshold)

Best-fit HOD parameters from Table 1 of Zheng et al. 2007.

Parameters:

threshold : float

Luminosity threshold defining the SDSS sample to which Zheng et al. fit their HOD model. Must be agree with one of the published values: [-18, -18.5, -19, -19.5, -20, -20.5, -21, -21.5, -22].

Returns:

parameter_dict : dict

Dictionary of model parameters whose values have been set to agree with the values taken from Table 1 of Zheng et al. 2007.