hmfast.halos.massdef.MassDefinition

class hmfast.halos.massdef.MassDefinition(delta=200, reference='critical')[source]

Bases: object

Mass definition for halos specified by an overdensity threshold and a reference density.

For example, \(M_{200c}\) corresponds to MassDefinition(delta=200, reference="critical"), while \(M_{200m}\) corresponds to MassDefinition(delta=200, reference="mean"). The special value delta='vir' denotes the redshift-dependent virial overdensity and can only be used with reference='critical'.

Attributes:

deltaint, float, or str: Overdensity threshold used to define the halo boundary. This can be a numeric value such as 200 or 500, or the string 'vir' for the redshift-dependent virial overdensity. The value 'vir' is only valid with reference='critical'.
referencestr: Reference density associated with delta, either 'critical' or 'mean'.

Raises:

ValueError: If an invalid combination of delta and reference is provided, or if either parameter is set to an unsupported value.

Methods

r_delta(cosmology, m, z)

Compute the halo radius \(r_\Delta\) associated with a halo mass.

r_delta(cosmology, m, z)[source]

Compute the halo radius \(r_\Delta\) associated with a halo mass.

\[r_\Delta = \left[\frac{3M}{4\pi \Delta \rho_{\mathrm{ref}}(z)}\right]^{1/3}\]

Parameters:

cosmologyCosmology: Cosmology object used to evaluate the reference density.
mfloat or array-like: Halo mass enclosed within the overdensity radius, in \(M_\odot\).
zfloat or array-like: Redshift at which to compute the radius.

Returns:

float or array-like: Radius \(r_\Delta\) within which the mean enclosed density is \(\Delta \rho_{\mathrm{ref}}(z)\), in physical \(\mathrm{Mpc}\). With shape \((N_m, N_z)\), where singleton dimensions get squeezed before return.