FRI radio galaxies at 1 < z < 2 Studying the building blocks of today ' s most massive galaxies and clusters by finding low luminosity radio galaxies at high - z Marco

Low luminosity “FRI” radio galaxies constitute by far the largest population of radio loud AGN in the local universe. They are invariably associated with the most massive elliptical galaxies, they are likely to possess supermassive black holes of 10 solar masses and higher and, differently for the more powerful “FRIIs”, they reside in rich clusters of galaxies. Therefore, they can be used as “beacons” to find high-z clusters and giant elliptical galaxies and study their formation and evolution. However, because of the tight luminosity-redshift dependence of flux limited samples, very few of those objects are known in the distant universe. We have recently selected a sample of 37 candidate low luminosity (FRI) radio galaxies at 1 < z < 2 in the COSMOS field using a multiwavelength selection technique. Larger samples can be selected in the future by applying similar criteria to surveys covering large sky areas. Our work opens the way for discovering and investigating galaxies and clusters associated with faint radio galaxies in the redshift range where traditional searching techniques (X-ray, optical/nearIR imaging) have struggled to yield solid cluster candidates to date. This clearly constitutes a pilot study for objects to be observed with future high-resolution and high-sensitivity instruments such as the EVLA and ALMA in the radio band, HST/WFC3 and 30m-class ground based telescopes in the optical and near-IR, JWST, as well as next generation X-ray satellites.