X-Ray Properties of Young Radio Quasars at z > 4.5
Abstract
We present a comprehensive analysis of Chandra X-ray observations of 15 young radio quasars at redshifts 4.5 < z < 5.0. All sources are detected in the 0.5-7.0 keV energy band. Emission spectra are extracted, and the average photon index for the sample is measured to be 1.5 ± 0.1. Unabsorbed rest-frame 2-10 keV luminosities are found to range between (0.5-23.2) × 1045 erg s-1. The optical-X-ray power-law spectral index ${\alpha }_{\mathrm{ox}}$ is calculated for each source using optical/UV data available in the literature. The ${\alpha }_{\mathrm{ox}}$ -UV relationship is compared with other quasar surveys, and an anticorrelation is observed that agrees with independent estimates. Rest-frame radio and X-ray luminosities are established for the sample, and a correlation between the luminosities is detected. These multiwavelength results reinforce a lack of spectral evolution for quasars over a broad redshift range. We additionally identify three quasars from our multiwavelength analysis that are statistically significant outliers, with one source being a Compton-thick candidate in the early universe, and discuss each in detail.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 2020
- DOI:
- 10.3847/1538-4357/aba2ca
- arXiv:
- arXiv:2007.01342
- Bibcode:
- 2020ApJ...899..127S
- Keywords:
-
- High-redshift galaxies;
- Active galactic nuclei;
- High energy astrophysics;
- Active galaxies;
- 734;
- 16;
- 739;
- 17;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- Accepted to ApJ, 13 pages, 5 figures, 4 tables