Blazars at the Cosmic Dawn

Abstract

The uncharted territory of the high-redshift (z 3) 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 z = 3. Our sample consists of 9 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 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 ( log M BH, M > 9) and luminous accretion disks ( L disk > 10 46 erg s −1 ). Their broadband spectral energy distributions are found to be dominated by high-energy radiation indicating their jets to be 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 the highredshift blazars may act as a reservoir for follow-up observations, e.g., with NuSTAR, to understand the evolution of relativistic jets at the dawn of the Universe.

X-ray constraints on the spectral energy distribution of the $z=5.18$ blazar SDSS J013127.34-032100.1

“…Note that the parameters in Table 2 are not very extreme. But given that B and δ for other highz (z=3-4) blazars are inferred to be modest (B=1-2 G and δ =10-16; Paliya et al 2020), the low-δ (e.g., <20) models may be preferred for J0131.…”

Radio signals from early direct collapse black holes

“…The assumed distributions do not have physical motivations, and they are rather empirically inspired; however we hope that they can provide at least a semi-quantitative estimate of the detectability. First, the combination of the Ghisellini et al ( , 2011; Ghisellini (2013); Ghisellini et al (2015); Paliya et al (2017Paliya et al ( , 2019Paliya et al ( , 2020 observed samples shows that the log 𝐵, Γ and log 𝑟 blob follow distributions similar to Gaussian shape, with log 𝐵 = 0.2, 𝜎 log 𝐵 = 0.2, Γ = 11, 𝜎 Γ = 2.5, and log 𝑟 blob = 1.9, 𝜎 log 𝑟 blob = 0.3. Since there is no any prior knowledges about jets of DCBHs, we borrow these statistics directly.…”

“…𝑟 blob ∼ 50 𝑟 𝑆 , 𝐵 ∼ 1 G, Γ ∼ 10, 𝛾 break ∼ 70 − 300, 𝛾 max ∼ 3000, and 𝑃 r /𝑃 jet ∼ 0.02 − 0.13. Paliya et al (2017Paliya et al ( , 2019Paliya et al ( , 2020 analyzed a sample of blazars and found 𝑟 blob ∼ 50 − 200 𝑟 𝑆 , 𝐵 ∼ 1 G, Γ ∼ 10, the spectrum index of the electrons distribution below 𝛾 break is ∼ 2 where 𝛾 break ∼ 100, and 𝑃 r /𝑃 jet ∼ 0.02 − 0.13. Motivated by the above observations, we adopt some jet parameter sets for the following investigation, see the jet 1, 2 and 3 listed in Tab.…”