%0 Journal Article
%A Marcotulli, L.
%A Paliya, Vaidehi Sharan
%A Ajello, M.
%A Kaur, A.
%A Marchesi, S.
%A Rajagopal, M.
%A Hartmann, D.
%A Gasparrini, D.
%A Ojha, R.
%A Madejski, G.
%T NuSTAR perspective on high-redshift MeV blazars
%J The astrophysical journal / 2
%V 889
%N 2
%@ 1538-4357
%C Chicago, Ill. [u.a.]
%I Univ.11032
%M PUBDB-2021-00238
%M arXiv:2001.01956
%P 164
%D 2020
%Z 17 pages, 7 figures, 8 tables, 1 appendix, accepted for publication in ApJ
%X With bolometric luminosities exceeding 10<sup>48</sup> erg s<sup>−1</sup>, 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 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 > 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 10<sup>9</sup> M<sub>\odot</sub> black holes, further raising the space density of supermassive black holes in the redshift bin z=[3,4].
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000537753200002
%R 10.3847/1538-4357/ab65f5
%U https://bib-pubdb1.desy.de/record/453874