Positions (skypy.position)

Uniform distributions

The simplest distribution of positions on the sky is the uniform distribution over a circular region with given centre and area. To sample this distribution, use the uniform_around function:

# survey information
survey_centre: !astropy.coordinates.SkyCoord [ '3h50m59.75s', '+54d39m22.15s' ]
survey_area: !astropy.units.Quantity [ '1000 deg2' ]

# sample 500 galaxies in survey
positions: !skypy.position.uniform_around
  centre: $survey_centre
  area: $survey_area
  size: 500

A more complicated uniform distribution is that over a given healpix pixel, which is sampled by the uniform_in_pixel function:

# healpix map information
nside: 2

# sample 500 galaxies in healpix pixel 5
positions: !skypy.position.uniform_in_pixel
  nside: $nside
  ipix: 5
  size: 500

Reference/API

skypy.position Package

Module for sampling positions on the sky.

Functions

uniform_around(centre, area, size)	Uniform distribution of points around location.
uniform_in_pixel(nside, ipix, size[, nest])	Uniform distribution of points over healpix pixel.