Blazars at the Cosmic Dawn
Vaidehi S. Paliya, M. Ajello, H. -M. Cao, M. Giroletti, Amanpreet, Kaur, Greg Madejski, Benoit Lott, D. Hartmann

TL;DR
This study identifies and characterizes high-redshift blazars, revealing their extreme luminosities, massive black holes, and fast jets, providing insights into early Universe quasar evolution.
Contribution
It presents a large multi-wavelength sample of $z>3$ blazars, including new observations, and analyzes their properties to understand jet evolution at cosmic dawn.
Findings
High-redshift blazars are faint gamma-ray emitters with steep spectra.
They host massive black holes and luminous accretion disks.
Jets in some sources exhibit higher bulk Lorentz factors.
Abstract
The uncharted territory of the high-redshift () Universe holds the key to understand the evolution of quasars. In an attempt to identify the most extreme members of the quasar population, i.e., blazars, we have carried out a multi-wavelength study of a large sample of radio-loud quasars beyond . Our sample consists of 9 -ray detected blazars and 133 candidate blazars selected based on the flatness of their soft X-ray spectra (0.310 keV photon index ), including 15 with NuSTAR observations. The application of the likelihood profile stacking technique reveals that the high-redshift blazars are faint -ray emitters with steep spectra. The high-redshift blazars host massive black holes () and luminous accretion disks ( erg s). Their broadband spectral energy…
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