early_type_lognormal_size¶
- skypy.galaxies.morphology.early_type_lognormal_size(magnitude, a, b, M0, sigma1, sigma2, size=None)[source] [edit on github]¶
Lognormal size distribution for early-type galaxies.
This function provides a lognormal distribution for the physical size of early-type galaxies, described by equations 12, 14 and 16 in [1].
- Parameters:
- magnitudefloat or array_like.
Galaxy magnitude at which evaluate the lognormal distribution.
- a, bfloat
Linear model parameters describing the mean size of galaxies, (Equation 14).
- sigma: float
Standard deviation of the lognormal distribution for the physical radius of galaxies.
- sizeint or tuple of ints, optional.
Output shape. If the given shape is, e.g., (m, n, k), then m * n * k samples are drawn. If size is None (default), a single value is returned if mean and sigma are both scalars. Otherwise, np.broadcast(mean, sigma).size samples are drawn.
- Returns:
- physical_sizendarray or astropy.Quantity
Physical distance for a given galaxy with a given magnitude, in [kpc]. If size is None and magnitude is a scalar, a single sample is returned. If size is ns, different from None, and magnitude is scalar, shape is (ns,). If magnitude has shape (nm,) and size=None, shape is (nm,).
References
[1]S. Shen, H.J. Mo, S.D.M. White, M.R. Blanton, G. Kauffmann, W. Voges, J. Brinkmann, I. Csabai, Mon. Not. Roy. Astron. Soc. 343, 978 (2003).