ryden04_ellipticity¶
- skypy.galaxies.morphology.ryden04_ellipticity(mu_gamma, sigma_gamma, mu, sigma, size=None)[source] [edit on github]¶
Ellipticity distribution of Ryden (2004).
The ellipticity is sampled by randomly projecting a 3D ellipsoid with principal axes \(A > B > C\) [1]. The distribution of the axis ratio \(\gamma = C/A\) is a truncated normal with mean \(\mu_\gamma\) and standard deviation \(\sigma_\gamma\). The distribution of \(\epsilon = \log(1 - B/A)\) is truncated normal with mean \(\mu\) and standard deviation \(\sigma\).
- Parameters
- mu_gammaarray_like
Mean of the truncated Gaussian for \(\gamma\).
- sigma_gammaarray_like
Standard deviation for \(\gamma\).
- muarray_like
Mean of the truncated Gaussian for \(\epsilon\).
- sigmaarray_like
Standard deviation for \(\epsilon\).
- sizeint or tuple of ints or None
Size of the sample. If
None
the size is inferred from the parameters.
- Returns
- ellipticity: (size,) array_like
Ellipticities sampled from the Ryden 2004 model.
References
- 1
Ryden B. S., 2004, ApJ, 601, 214