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| gdouble | nc_halo_bias_eval () |
| void | nc_halo_bias_free () |
| void | nc_halo_bias_clear () |
| gdouble | nc_halo_bias_integrand () |
GObject ╰── NcHaloBias ├── NcHaloBiasPS ├── NcHaloBiasSTEllip ├── NcHaloBiasSTSpher ╰── NcHaloBiasTinker
Abstract object to compute the halo bias function given a mass function. The bias function is given by the eval function, which should be implemented by the child objects of the NcHaloBias class. Below there is a quick review about dark matter halo bias.
Dark Matter Halos are tracers of the Large Scale Structure (LSS) of the universe. On sufficient large scales, the correlations are weak and these objects are expected to be well described by perturbation theory. Given the background matter distribution, $\rho$, one can assume that the mass distribution in the universe is given by a small perturbation around this value. In this context, we define the density contrast $\delta$ as
\begin{align} \delta_b &= \frac{\delta \rho}{\rho} ,\end{align} which represents this perturbation around the background quantity.
The halos are formed when the density contrast passes a certain critical limit, that is, $\delta_b > \delta_c$. Even though $\delta_b$ is a gaussian random field, the real cluster formation is a rare event that involves non-linear mechanisms that cannot be explained perturbatively, and thus we must consider Peak-Background split effects. To connect the theory to observations, we introduce "bias parameters" in the observed halos distributions.
These bias parameters are linear corrections to the density contrast field, such that \begin{align} \delta &= [1 + b(z, M)] \delta_b ,\end{align} where $\delta$ is the new density contrast that accounts for the bias and $b(z, M)$ is the bias. There different biases for each mass function used in the cosmological computations. Check the child objects for their definitions.
Since this is an abstract class implementation, there is no initialization function of the object.
gdouble nc_halo_bias_eval (NcHaloBias *bias,NcHICosmo *cosmo,gdouble sigma,gdouble z);
Computes the Halo Bias at a given redshift.
void
nc_halo_bias_free (NcHaloBias *bias);
Atomically decrements the reference count of bias
by one. If the reference count drops to 0,
all memory allocated by bias
is released.
void
nc_halo_bias_clear (NcHaloBias **bias);
Atomically decrements the reference count of bias
by one. If the reference count drops to 0,
all memory allocated by bias
is released. Set pointer to NULL.
gdouble nc_halo_bias_integrand (NcHaloBias *mbiasf,NcHICosmo *cosmo,gdouble lnM,gdouble z);
This function is the integrand of the mean bias, i.e., the product of the mass function with the bias function. As both functions depend on the standard deviation of the matter density contrast, we implement this function to compute \f$ \sigma (M, z) \f$ just once.
It is worth noting that the multiplicity function must be compatible with the bias function.
“mass-function” property“mass-function” NcHaloMassFunction *
This property keeps the mass function object.
Owner: NcHaloBias
Flags: Read / Write / Construct Only