GNU Astronomy Utilities - Bugs: bug #65254, Non-flat cases of angular diameter...
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bug #65254: Non-flat cases of angular diameter distance
Submitter: | Boud Roukema <boud> | ||
Submitted: | Sun 04 Feb 2024 04:26:25 PM UTC | ||
Category: | CosmicCalculator | Severity: | 3 - Normal |
Item Group: | Output not reasonable | Status: | None |
Privacy: | Public | Assigned to: | None |
Open/Closed: | Open |
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Depends on the following items: None found
Items that depend on this one: None found
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Follows 1 latest change.
Date | Changed by | Updated Field | Previous Value | => | Replaced by |
---|---|---|---|---|---|
2024-02-04 | boud | Category | None | CosmicCalculator |
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Corresponding source code
PROBLEM: Gnuastro 0.22.1-bc3d calculates the comoving one-radian arclength (= the "areal radius" = the "proper motion distance"), and the corresponding physical-units one-radian arclength that is usually called the "angular diameter distance", and other parameters deriving from this, on the assumption that the FLRW model is flat. This is incorrect for non-flat models. This implies that:
are all wrong in the non-flat cases. This error was mentioned earlier in bug #65195 [1].)
TASK: Introduce a function equivalent to cosm_get_pm_dist in cosmdist 0.3.12 (GPL-2+) [2] to calculate the comoving one-radian arclength based on the radial comoving distance (currently called 'proper_distance' in gnuastro, which is acceptable) and the cosmology curvature parameter. Then functions such as gal_cosmology_angular_distance will need to be corrected.
CHECK:
These checks are for cosmdist 0.3.12 and gnuastro 0.22.1-bc3d, showing that only the flat case (olambda+omatter+oradiation = 1) for astcosmiccal is currently correct; the non-flat cases are wrong.
Comoving tangential one-radian arclength:
Angular diameter distance:
Luminosity distance:
[1] https://savannah.gnu.org/bugs/?65195
[2] https://codeberg.org/boud/cosmdist/src/branch/main/lib/get_pm_dist.c