Blazars at the Cosmic Dawn
Abstract
The uncharted territory of the high-redshift (z ≳ 3) universe holds the key to understanding the evolution of quasars. In an attempt to identify the most extreme members of the quasar population, that is, blazars, we have carried out a multiwavelength study of a large sample of radio-loud quasars beyond z = 3. Our sample consists of nine γ-ray-detected blazars and 133 candidate blazars selected based on the flatness of their soft X-ray spectra (0.3-10 keV photon index ≤1.75), including 15 with Nuclear Spectroscopic Telescope Array (NuSTAR) observations. The application of the likelihood profile stacking technique reveals that the high-redshift blazars are faint γ-ray emitters with steep spectra. The high-redshift blazars host massive black holes ( $\langle \mathrm{log}\,{M}_{\mathrm{BH},M\odot }\rangle \gt 9$ ) and luminous accretion disks ( $\langle {L}_{\mathrm{disk}}\rangle \gt {10}^{46}$ erg s-1). Their broadband spectral energy distributions are found to be dominated by high-energy radiation, indicating their jets are among the most luminous ones. Focusing on the sources exhibiting resolved X-ray jets (as observed with the Chandra satellite), we find the bulk Lorentz factor to be larger with respect to other z > 3 blazars, indicating faster moving jets. We conclude that the presented list of high-redshift blazars may act as a reservoir for follow-up observations, such as with NuSTAR, to understand the evolution of relativistic jets at the dawn of the universe.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2020
- DOI:
- arXiv:
- arXiv:2006.01857
- Bibcode:
- 2020ApJ...897..177P
- Keywords:
-
- Blazars;
- Active galactic nuclei;
- High-redshift galaxies;
- Radiative processes;
- 734;
- 16;
- 2055;
- 164;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- To appear in the Astrophysical journal. Full tables and plots are provided