The Age of the Universe, the Hubble Constant and QSOs in a Locally Inhomogeneous Universe

Abstract

A local void in the globally Friedmann-Robertson-Walker cosmological model with the critical density ($\Omega_{0}=1$) is studied. The inhomogeneity is described using a Lema\^{\i}tre-Tolman-Bondi solution for a spherically symmetric distribution of matter. The scale of the central underdense region is $\sim 150$ Mpc. We investigate the effects this has on the cosmological time scale, the measurement of the Hubble constant and the redshift--luminosity distance for moderately and very distant objects ($z \sim 0.1$ and more). The results indicate that if we happened to live in such a void, but insisted on interpreting cosmological observations through the FRW model, we could go wrong in a few instances. For example, the Hubble constant measurement could give results depending on the separation of the source and the observer, the quasars could be younger than we think and also less distant (less energetic).