paper

Model-independent Distance Calibration and Curvature Measurement using Quasars and Cosmic Chronometers

arXiv:1912.00668 · doi:10.3847/1538-4357/ab5e7d

Abstract

We present a new model-independent method to determine the spatial curvature and to mitigate the circularity problem affecting the use of quasars as distance indicators. The cosmic-chronometer measurements are used to construct the curvature-dependent luminosity distance using a polynomial fit. Based on the reconstructed and the known ultraviolet versus X-ray luminosity correlation of quasars, we simultaneously place limits on the curvature parameter and the parameters characterizing the luminosity correlation function. This model-independent analysis suggests that a mildly closed Universe () is preferred at the level. With the calibrated luminosity correlation, we build a new data set consisting of 1598 quasar distance moduli, and use these calibrated measurements to test and compare the standard CDM model and the universe. Both models account for the data very well, though the optimized flat CDM model has one more free parameter than , and is penalized more heavily by the Bayes Information Criterion. We find that is slightly favoured over CDM with a likelihood of versus 42.3\%.

8 pages, 5 figures, 2 tables. Accepted for publication in ApJ

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