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- Astropy v5.2.1 »
- Cosmological Calculations (`astropy.cosmology`) »
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- redshift_distance

# redshift_distance

astropy.cosmology.units.redshift_distance(cosmology=None, kind='comoving', **atzkw)

  Convert quantities between redshift and distance.

  Care should be taken to not misinterpret a relativistic, gravitational, etc redshift as a cosmological one.

  Parameters:
    cosmology `Cosmology`, `python:str`, or `python:None`, optional

      A cosmology realization or built-in cosmology’s name (e.g. ‘Planck18’). If None, will use the default cosmology (controlled by `default_cosmology`).

    kind{‘comoving’, ‘lookback’, ‘luminosity’} or `python:None`, optional

      The distance type for the Equivalency. Note this does NOT include the angular diameter distance as this distance measure is not monotonic.

    **atzkw

      keyword arguments for `z_at_value()`

  Returns:
    `Equivalency`

      Equivalency between redshift and temperature.

  Examples

      >>> import astropy.units as u
      >>> import astropy.cosmology.units as cu
      >>> from astropy.cosmology import WMAP9

      >>> z = 1100 * cu.redshift
      >>> z.to(u.Mpc, cu.redshift_distance(WMAP9, kind="comoving"))
      <Quantity 14004.03157418 Mpc>