NuSTAR perspective on high-redshift MeV blazars [article]

L. Marcotulli, V. Paliya, M. Ajello, A. Kaur, S. Marchesi, M. Rajagopal, D. Hartmann, D. Gasparrini, R. Ojha, G. Madejski, Maryland Shared Open Access Repository, Maryland Shared Open Access Repository
2020
With bolometric luminosities exceeding 10⁴⁸ 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 NuSTAR, Swift and SARA observations. We observe six
more » ... e 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 re-hardening of the X-ray spectrum at energies E>6keV. 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 10⁹M⊙ black holes, further raising the space density of supermassive black holes in the redshift bin z=[3,4].
doi:10.13016/m24tyn-b9ik fatcat:4mxhfcqbe5hojaxzsn577vxufy