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The first blazar observed at z>6
S. Belladitta, A. Moretti, A. Caccianiga +9
We present the discovery of PSO J030947.49+271757.31, the radio brightest (23.7 mJy at 1.4 GHz) active galactic nucleus (AGN) at z>6.0. It was selected by cross-matching the NRAO V…
Radio-loud AGNs at high redshifts and the cosmic microwave background
G. Ghisellini, A. Celotti, F. Tavecchio +2
We discuss how the interaction between the electrons in a relativistic jet and the Cosmic Microwave Background (CMB) affects the observable properties of radio-loud AGN at early ep…
NuSTAR detection of the blazar B2 1023+25 at redshift 5.3
T. Sbarrato, G. Tagliaferri, G. Ghisellini +19
B2 1023+25 is an extremely radio-loud quasar at z=5.3 which was first identified as a likely high-redshift blazar candidate in the SDSS+FIRST quasar catalog. Here we use the Nuclea…
The role of relativistic jets in the heaviest and most active supermassive black holes at high redshift
G. Ghisellini, F. Haardt, R. Della Ceca +2
In powerful radio-quiet active galactic nuclei (AGN), black holes heavier than one billion solar masses form at a redshift ~1.5-2. Supermassive black holes in jetted radio-loud AGN…
Blazar candidates beyond redshift 4 observed with GROND
T. Sbarrato, G. Ghisellini, M. Nardini +4
The search for extremely massive high redshift blazars is essential to put strong constraints on the supermassive black holes formation theories. Up to now, the few blazars known t…
High redshift Fermi blazars observed by GROND and Swift
G. Ghisellini, M. Nardini, G. Tagliaferri +7
We observed 5 gamma-ray loud blazars at redshift greater than 2 with the X-Ray Telescope (XRT) and the UltraViolet and Optical Telescope (UVOT) onboard the Swift satellite, and the…
SDSS J102623.61+254259.5: the second most distant blazar at z=5.3
T. Sbarrato, G. Ghisellini, M. Nardini +7
The radio-loud quasar SDSS J102623.61+254259.5, at a redshift z=5.3, is one of the most distant radio-loud objects. Since its radio flux exceeds 100 mJy at a few GHz, it is also on…
Blue Fermi Flat Spectrum Radio Quasars
G. Ghisellini, F. Tavecchio, L. Foschini +3
Many blazars detected by the Fermi satellite, observed spectroscopically in the optical, are line-less, and have been classified as BL Lac objects. Optical-UV photometry of nearly…
The WISE view of the disc-torus connection in z~0.6 Active Galactic Nuclei
Giorgio Calderone, Tullia Sbarrato, Gabriele Ghisellini
We selected all radio-quiet AGN in the latest release of Sloan digital sky survey quasar catalog, with redshift in the range 0.56-0.73. About 4000 (~80%) of these have been detecte…