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ANGSIZ: A general and practical method for calculating
cosmological distances
Phillip Helbig 1,
Rainer Kayser, &
Thomas Schramm
1
University of Manchester, NRAL
Abstract:
The calculation of distances is of fundamental importance
in extragalactic astronomy and cosmology. However, no
practical implementation for the general case has previously
been available. We derive a second-order differential equation
for the angular size distance valid not only in all homogeneous
Friedmann-Lemaitre cosmological models, parametrised by
$\lambda_{0}$ and $\Omega_{0}$, but also in inhomogeneous
`on-average' Friedmann-Lemaitre models, where the
inhomogeneity is given by the (in the general case redshift-dependent)
parameter $\eta$. Since most other distances can be obtained trivially
from the angular size distance, and since the differential equation
can be efficiently solved numerically, this offers for the first time a
practical method for calculating distances in a large class of
cosmological models. We also briefly discuss our numerical
implementation, which is publicly available.
Subject headings: cosmology: theory - distance scale - gravitational lensing
Latest Version: 1997 October 12
Archived: 1999 September 8
Papers:
Kayser, R., Helbig, P., & Schramm, T., 1997A&A...318..680K
Preprint:
astro-ph/9603028
Language: Fortran
External Explanatory Pages:
http://multivac.jb.man.ac.uk:8000/helbig/research/publications/Info/angsiz.html
Source Code:
all_angsiz.for