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M. Karovska, M. Elvis (CfA)
Recently we proposed a new geometric method for measuring distances to quasars, and thereby determining the metric of the universe. This "quasar parallax" method uses the physical size of the quasar Broad Emission Line Region (BELR) derived from reverberation mapping combined with the angular size of the BELR derived from interferometric measurements to derive distances to quasars at different redshifts. A byproduct of these studies will be complete velocity-resolved imaging of the inner regions of quasars, directly resolving decades of debate.
To measure the angular sizes of BELRs we need a long-baseline interferometer with a submilliarcsecond (0.1-0.01mas) resolution and with the capability to observe selected quasar emission lines repeatedly. Reverberation mapping shows that UV emission lines [e.g. CIV (1550A), Mg II H&K (2800A), Ly-alpha (1215A)] are the most favorable for BELR size measurements. Neither currently, nor in the near future, is there any ground- or space-based telescope or interferometer with the resolution needed to resolve the BELR in these lines. We describe an application of our method using the Stellar Imager (SI) - a Vision mission in the Sun-Earth Connection (SEC) Roadmap. This 500m long baseline UV interferometer will have a unique capability to image directly the quasar BELR in several UV lines and the continuum and to determine the distances to redshifts of z~1. We will show examples of BELR diameter measurements and simulations of sparse aperture imaging of quasars at different redshifts.
This work was supported by NASA contracts NAS8-39073 and NAS8-03060.
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Bulletin of the American Astronomical Society, 36 #2
© YEAR. The American Astronomical Soceity.