Open AccessThe Δθ– z s relation for gravitational lenses as a cosmological test
Author(s) -
Helbig Phillip
Publication year - 1998
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1998.01692.x
Subject(s) - physics , redshift , universe , astrophysics , gravitation , sign (mathematics) , metric expansion of space , shape of the universe , theoretical physics , cosmology , astronomy , dark energy , galaxy , mathematical analysis , mathematics
Recently, Park &38; Gott claimed that there is a statistically significant, strong, negative correlation between the image separation Δθ and source redshift z s for gravitational lenses. This is somewhat puzzling if one believes in a flat ( k = 0) universe, since in this case the typical image separation is expected to be independent of the source redshift, while one expects a negative correlation in a k = −1 universe and a positive one in a k = +1 universe. Park &38; Gott explored several effects that could cause the observed correlation, but no combination of these can explain the observations with a realistic scenario. Here, I explore this test further in three ways. First, I show that in an inhomogeneous universe a negative correlation is expected regardless of the value of k . Secondly, I test whether the Δθ– z s relation can be used as a test to determine λ 0 and Ω 0 , rather than just the sign of k . Thirdly, I compare the results of the test from the Park &38; Gott sample with those using other samples of gravitational lenses, which can illuminate (unknown) selection effects and probe the usefulness of the Δθ– z s relation as a cosmological test.