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).