NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-08-18 T02:51:16 PDT
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For refcode 2014ApJ...787L..12L:
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2014ApJ...787L..12L A New Cosmological Distance Measure Using Active Galactic Nucleus X-Ray Variability La Franca, Fabio; Bianchi, Stefano; Ponti, Gabriele; Branchini, Enzo; Matt, Giorgio Abstract. We report the discovery of a luminosity distance estimator using active galactic nuclei (AGNs). We combine the correlation between the X-ray variability amplitude and the black hole (BH) mass with the single-epoch spectra BH mass estimates which depend on the AGN luminosity and the line width emitted by the broad-line region. We demonstrate that significant correlations do exist that allow one to predict the AGN (optical or X-ray) luminosity as a function of the AGN X-ray variability and either the Hbeta or the Pabeta line widths. In the best case, when the Pabeta is used, the relationship has an intrinsic dispersion of ~0.6 dex. Although intrinsically more disperse than supernovae Ia, this relation constitutes an alternative distance indicator potentially able to probe, in an independent way, the expansion history of the universe. With respect to this, we show that the new mission concept Athena should be able to measure the X-ray variability of hundreds of AGNs and then constrain the distance modulus with uncertainties of 0.1 mag up to z ~ 0.6. We also discuss how our estimator has the prospect of becoming a cosmological probe even more sensitive than the current supernovae Ia samples by using a new dedicated wide-field X-ray telescope able to measure the variability of thousands of AGNs. Key words: cosmological parameters, cosmology: observations, distance scale, galaxies: active, X-rays: general
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