Behroozi10SmHm¶
- class halotools.empirical_models.Behroozi10SmHm(**kwargs)[source]¶
Bases:
PrimGalpropModel
Stellar-to-halo-mass relation based on Behroozi et al 2010.
Note
The
Behroozi10SmHm
model is part of thebehroozi10
prebuilt composite subhalo-based model. For a tutorial on thebehroozi10
composite model, see Behroozi et al. (2010) Composite Model.- Parameters:
- prim_haloprop_keystring, optional
String giving the column name of the primary halo property governing stellar mass. Default is set in the
model_defaults
module.- scatter_modelobject, optional
Class governing stochasticity of stellar mass. Default scatter is log-normal, implemented by the
LogNormalScatterModel
class.- scatter_abscissaarray_like, optional
Array of values giving the abscissa at which the level of scatter will be specified by the input ordinates. Default behavior will result in constant scatter at a level set in the
model_defaults
module.- scatter_ordinatesarray_like, optional
Array of values defining the level of scatter at the input abscissa. Default behavior will result in constant scatter at a level set in the
model_defaults
module.- redshiftfloat, optional
Redshift of the stellar-to-halo-mass relation. Recommended default behavior is to leave this argument unspecified.
If no
redshift
argument is given to the constructor, you will be free to use the analytical relations bound toBehroozi10SmHm
to study the redshift-dependence of the SMHM by passing in aredshift
argument to themean_log_halo_mass
andmean_stellar_mass
methods.If you do pass a
redshift
argument to the constructor, the instance of theBehroozi10SmHm
will only return results for this redshift, and will raise an exception if you attempt to pass in a redshift to these methods. See the Notes below to understand the motivation for this behavior.
Notes
Note that the
Behroozi10SmHm
class is a distinct from theBehroozi10
model in several respects. The most important distinction to understand is thatBehroozi10
is a composite model that has been built to populate simulations with mock galaxies, whereasBehroozi10SmHm
is a component model that is just a collection of analytical functions.Related to the above, the
Behroozi10
composite model has a single redshift hard-wired into its behavior to guarantee consistency with the halo catalog into whichBehroozi10
will sprinkle mock galaxies. On the other hand, theBehroozi10SmHm
model need not have aredshift
attribute bound to it at all, which permits you to use the analytical functions bound toBehroozi10SmHm
to study the redshift-dependence of the stellar-to-halo-mass relation. However, since theBehroozi10
composite model uses an instance of theBehroozi10SmHm
for its stellar-to-halo-mass feature, then there must be some mechanism by which the redshift-dependence of theBehroozi10SmHm
can be held fixed. The option to provide a specific redshift to the constructor ofBehroozi10SmHm
provides this mechanism.Methods Summary
mean_log_halo_mass
(log_stellar_mass, **kwargs)Return the halo mass of a central galaxy as a function of the stellar mass.
mean_stellar_mass
(**kwargs)Return the stellar mass of a central galaxy as a function of the input table.
Method returns a dictionary of all model parameters set to the column 2 values in Table 2 of Behroozi et al. (2010).
Methods Documentation
- mean_log_halo_mass(log_stellar_mass, **kwargs)[source]¶
Return the halo mass of a central galaxy as a function of the stellar mass.
- Parameters:
- log_stellar_massarray
Array of base-10 logarithm of stellar masses in h=1 solar mass units.
- redshiftfloat or array, optional
Redshift of the halo hosting the galaxy. If passing an array, must be of the same length as the input
log_stellar_mass
. Default is set insim_defaults
.
- Returns:
- log_halo_massarray_like
Array containing 10-base logarithm of halo mass in h=1 solar mass units.
Notes
The parameter values in Behroozi+10 were fit to data assuming h=0.7, but all halotools inputs are in h=1 units. Thus we will transform our input stellar mass to h=0.7 units, evaluate using the behroozi parameters, and then transform back to h=1 units before returning the result.
- mean_stellar_mass(**kwargs)[source]¶
Return the stellar mass of a central galaxy as a function of the input table.
- Parameters:
- prim_haloproparray, optional
Array of mass-like variable upon which occupation statistics are based. If
prim_haloprop
is not passed, thentable
keyword argument must be passed.- tableobject, optional
Data table storing halo catalog. If
table
is not passed, thenprim_haloprop
keyword argument must be passed.- redshiftfloat or array, optional
Redshift of the halo hosting the galaxy. If passing an array, must be of the same length as the input
stellar_mass
. Default is set insim_defaults
.
- Returns:
- mstararray_like
Array containing stellar masses living in the input table, in solar mass units assuming h = 1.