Affiliation: INAF-Brera

Contribution: Oral

Title: Relativistic jets from QSOs in the early Universe

Abstract: How the supermassive black holes (SMBHs) we detect in the early Universe formed and grew to the observed sizes in such a short period of time is still not clear. One possible explanation could be given by the presence of relativistic jets that may significantly increase the growth efficiency. However, the actual number and the properties of “jetted QSOs” (usually dubbed as radio-loud, RL) at high redshift is still poorly constrained, due to low statistics. In this talk I will describe our efforts in characterising the evolution of the high-z RL QSO population. In particular, I will present the selection of the largest well-defined sample of RL QSOs at z>5 currently available, containing 31 objects, built from the combination of some of the deepest wide-area surveys currently available: RACS, in the radio, and DES/PanSTARRS, in the optical/NIR. This sample can now be used in order to firmly constrain the redshift evolution of this population (in terms of emission and obscuration) and of their space density. At the same time, I will also describe how dedicated multi-wavelength (radio, NIR and X-ray) observations of these sources are essential in order to help constrain the properties of the SMBHs and jets hosted in these extreme systems. Finally, I will show how future surveys (EMU, LSST, EUCLID) will allow us to push these studies to unprecedented redshifts.

This contribution can be found here (pdf).