Search for high-redshift blazars with Fermi/LAT

Author/Creator ORCID





Citation of Original Publication

Kreter, Michael; Kadler, Matthias; Krauß, Felicia; Buson, Sara; Ojha, Roopesh; Fermi/LAT Collaboration; Wilms, Jörn; Böttcher, Markus; Search for high-redshift blazars with Fermi/LAT; 36th International Cosmic Ray Conference -ICRC2019;


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High-redshift blazars (z ≥ 2.5) are one of the most powerful classes of γ-ray sources in the Universe. These objects possess the highest jet powers and luminosities and have black-hole masses often in excess of 10⁹ solar masses. In addition, high-redshift blazars are important cosmological probes and serve as test objects for blazar evolution models. Due to their large distance, their high-energy emission peaks are often downshifted to energies below the GeV range, which makes them difficult to study with Fermi/LAT and only the very brightest objects are detectable. Hence, only a small number of high-redshift blazars could be detected with Fermi/LAT so far. In this work, we present a strategy to increase the detection statistics at redshift z ≥ 2.5 via a search for flaring events in high-redshift γ-ray blazars whose long-term flux is just below the sensitivity limit of Fermi/LAT. Seven previously GeV undetected high-redshift blazars have been identified from their bright monthly outburst periods, while more detections are expected in the future.