angular_size

skypy.galaxy.size.angular_size(physical_size, redshift, cosmology)[source] [edit on github]

Angular size of a galaxy. This function transforms physical radius into angular distance, described in [1].

Parameters
physical_sizeastropy.Quantity

Physical radius of galaxies in units of length.

redshiftfloat

Redshifts at which to evaluate the angular diameter distance.

cosmologyastropy.cosmology.Cosmology

Cosmology object providing methods for the evolution history of omega_matter and omega_lambda with redshift.

Returns
angular_sizeastropy.Quantity

Angular distances in units of [rad] for a given radius.

References

1

    1. Hogg, (1999), astro-ph/9905116.

Examples

>>> from astropy import units
>>> from skypy.galaxy.size import angular_size
>>> from astropy.cosmology import Planck15
>>> r = angular_size(10*units.kpc, 1, Planck15)