Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993apj...419...12k&link_type=abstract
Astrophysical Journal v.419, p.12
Astronomy and Astrophysics
Astronomy
148
Cosmology: Observations, Galaxies: Distances And Redshifts, Galaxies: Structure, Cosmology: Gravitational Lensing
Scientific paper
We do a maximum likelihood analysis of three optical surveys for gravitational lenses. The results are consistent with lensing by normal galaxies modeled as singular isothermal spheres with standard values for observational parameters, aside from the need to add a small amount of ellipticity to produce the observed four image lenses. We tested the model for variations ill the number of galaxies, the velocity dispersions of galaxies, the distribution of galaxies, the relation between luminosity and velocity dispersion, the quasar apparent magnitude number counts, and the mean magnification produced by the lenses. No variation we examined significantly improved the likelihoods over using the standard observational values, although there is weak evidence for differences in the magnification bias. The measured isothermal velocity dispersion of an L* E/S0 galaxy is σ*=245 km s-1 with a 90% confidence interval of 210 km s-1 ≲ σ* ≲ 270 km s-1, ignoring the lens 0957+561. This is consistent with the estimated range from dynamical studies of 183-248 km s-1. The measured comoving density of galaxies or dark halos on this mass scale is 6.7 × 10-3h3 Mpc-3 with a 90% confidence interval from 2.0 × 10-3h3 Mpc3 to 1.7 x 10-3h3 Mpc-3. Depending on systematic assumptions about treating the lens 0957+561 and the contribution of spiral galaxies to lensing, the upper limit on the value of the cosmological constant can be as high as ΩΛ ≲ 0.8 or as low as ΩΛ ≲ 0.45. Doubling the sample size will reduce the confidence intervals to levels where contradictions with other observations may become apparent.
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