NuSTAR Perspective on High-redshift MeV Blazars
L. Marcotulli, V. Paliya, M. Ajello, A. Kaur, S. Marchesi, M. Rajagopal, D. Hartmann, D. Gasparrini, R. Ojha, G. Madejski
Abstract
Abstract With bolometric luminosities exceeding 10 48 erg s −1 , powerful jets, and supermassive black holes at their center, MeV blazars are some of the most extreme sources in the universe. Recently, the Fermi -Large Area Telescope detected five new γ -ray emitting MeV blazars beyond redshift z = 3.1. With the goal of precisely characterizing the jet properties of these extreme sources, we started a multiwavelength campaign to follow them up with joint Nuclear Spectroscopic Telescope Array , Swift, and the Southeastern Association for Research in Astronomy’s optical telescopes. We observe six high-redshift quasars, four of them belonging to the new γ -ray emitting MeV blazars. Thorough X-ray analysis reveals spectral flattening at soft X-ray for three of these objects. The source NVSS J151002+570243 also shows a peculiar rehardening of the X-ray spectrum at energies E > 6 keV. Adopting a one-zone leptonic emission model, this combination of hard X-rays and γ -rays enables us to determine the location of the Inverse Compton peak and to accurately constrain the jet characteristics. In the context of the jet-accretion disk connection, we find that all six sources have jet powers exceeding accretion disk luminosity, seemingly validating this positive correlation even beyond z > 3. Our six sources are found to have black holes, further raising the space density of supermassive black holes in the redshift bin z = [3, 4].