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Exotic Quasars in the Early Universe
Bradford Snios (Smithsonian Astrophysical Observatory)
Tuesday 20/04/2021 @ 14:00, Sala IV piano Battiferro
Studies of high-redshift quasars provide new opportunities to investigate evolutionary properties of the Universe, and X-ray observations are uniquely adept at constraining these properties. In my talk, I report a recent analysis of Chandra X-ray observations of 15 young radio quasars at redshifts 4.5 < z < 5.0. The optical–X-ray power-law spectral index as well as the rest-frame radio-X-ray luminosities are derived for the quasar sample, and overall trends are discussed. From the multiwavelength analysis, several outliers within the sample are identified. In particular, I highlight the discovery of a heavily obscured quasar candidate in the early Universe at z=4.56. Based on the X-ray spectroscopic analysis, the source has an estimated obscuring column density in excess of 10**24 / cm**2, making it the fourth known Compton-thick quasar at z > 4.