A Catalog of Active Galactic Nuclei from the First 1.5 Gyr of the Universe

Abstract

Active galactic nuclei (AGN) are prominent astrophysical objects that can be observed throughout the whole Universe. To understand the underlying physical processes and the different appearance of AGN types, extensive samples are needed. Nowadays, various AGN catalogs are available at different wavebands. However, at the highest redshifts data are still relatively sparse. These data are required for examining AGN properties in the early Universe. This way we can compare the earliest AGN with those seen at lower redshifts, and can study their cosmological evolution. Additionally, because of their high luminosity, AGN may also be used as probes to test cosmological models. With the aim of constructing a complete sample of all known AGN at z ≥ 4, we are currently compiling a photometric catalog from literature sources. We cross-match catalogs particularly at optical and radio wavebands, to build up a sample for detailed high-resolution radio interferometric studies. The continuously updated list now contains nearly 2,600 objects with known spectroscopic redshifts, optical magnitudes, and auxiliary information about observations at other wavebands. About 170 of them are known radio sources for which we collect existing radio interferometric data from the literature.

Fast jet proper motion discovered in a blazar at z=4.72

“…The fact that only ∼ 10% of the optically detected quasars are radio-loud, and that radio-loud quasars become too weak to be detected by radio telescopes at very large cosmological distances make high-redshift radio-loud quasars much more rare. The number of radio-detected AGNs with available spectroscopic redshift at z > 4 is only about 170 [7], and the most distant radio-loud quasar to date is J1429+5447 at z = 6.21 [8,9].…”

Unveiling the weak radio quasar population at $z\ge 4$

“…Since the discovery of the first quasar at redshift z ≥ 4 (Warren et al 1987), the number of active galactic nuclei (AGN) known at the highest redshifts is continuously increasing. As a result of extensive observing campaigns and surveys (e.g., York et al 2000;Wright et al 2010;Eisenstein et al 2011;Chambers et al 2016;Dark Energy Survey Collaboration et al 2016;Blanton et al 2017), there are nearly 3000 sources identified between z = 4 and z = 7.54 to date, yet only ∼ 6.5 per cent of these exhibit radio emission (Perger et al 2017) detected at 1.4 GHz by either the Very Large Array (VLA) Faint Images of the Radio Sky at Twenty-Centimeters 1 (FIRST, Becker, White & Helfand 1995;Helfand, White & Becker 2015) survey or the National Radio Astronomy Observatory (NRAO) VLA Sky Survey 2 (NVSS, Condon et al 1998). The remaining sources are either outside the footprint of ⋆ E-mail: k.perger@astro.elte.hu 1 http://sundog.stsci.edu/ 2 https://www.cv.nrao.edu/nvss/ both FIRST and NVSS, or are below the detection limit of the two surveys.…”

High-resolution radio imaging of two luminous quasars beyond redshift 4.5

“…They are also rare because of the limited sensitivity of our instruments. For example, the number of known AGN with measured spectroscopic redshift at z > 4 is nearly 2600, and only about 170 are known radio sources (Perger et al 2017). In comparison, the total number of AGN is now close to a million (Flesh 2015).…”