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M. Karovska, M. Elvis (Harvard-Smithsonian CfA)
Recent distance measurements using the brightness of supernovae of type 1a as `standard candles' suggest that the universe has a non-zero cosmological constant, \Lambda. An independent confirmation of such an important measurement is clearly important. Here we propose a method, equivalent to geometric parallax, to determine distances to radio-quiet quasars. Quasar Broad Emission Line Regions (BELRs) sizes provide a `meter rule' with which to measure the metric of the Universe. We present a new approach for determining distances to quasars using a time delay method for estimating the linear sizes of BELRs (reverberation mapping) combined with interferometric measurements of their angular sizes. By measuring the BELRs `angular diameter' to a series of quasars at different redshifts the `angular diameter distance', can be mapped out against redshift. The resulting angular-diameter vs. redshift relation is a basic characteristic of the space-time metric of the Universe. From this relation we can determine \Lambda. We discuss feasibility issues related to reverberation mapping and angular measurements using long baseline interferometers from X-ray to IR wavelengths.
This work was supported in part by NASA contract NAS8-39073 (Chandra X-ray Center).
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.