uvex_transients.utils.cosmology.physical_to_angular#

uvex_transients.utils.cosmology.physical_to_angular(size: Quantity, redshift: float | NDArray[float64] | None = None, cosmology: Cosmology | None = None) → Quantity[source]#

Convert a physical transverse size to an angular size.

Parameters:

  • size (~astropy.units.Quantity) – Physical transverse size.

  • redshift (float) – Redshift of the object.

  • cosmology (~astropy.cosmology.FLRW, optional) – Cosmology used to compute the angular diameter distance. If None, the configured default cosmology is used.

Returns:

Angular size corresponding to the physical extent.

Return type:

~astropy.units.Quantity

Notes

The angular size is given by

\[\theta = \frac{s}{D_A}\]

where \(D_A\) is the angular diameter distance.

Examples

>>> import astropy.units as u
>>> physical_to_angular(10 * u.kpc, redshift=0.5)
<Quantity 1.58957339 arcsec>