Multi-frequency studies of very high energy peaked blazars

Observations have shown that blazars (a special sub-class of active galactic nuclei) of the high synchrotron peak type (HSPs) play a crucial role in TeV/Very High Energy (VHE) astronomy. To provide a large list of potential VHE emitters, and therefore candidate targets for current and future TeV instruments, we have assembled a catalog including over 2000 confirmed and candidate HSP blazars selected on the basis of multi-frequency data. The catalog, named 3HSP, is currently the largest and most complete sample of HSP blazars, and can be used for detailed statistical properties of the whole HSP population and may shed light on some of the the long-standing issues in the cosmological evolution of blazars. The most recent successful case is a new TeV source, PGC 2402248, was detected by the MAGIC (Major Atmospheric Gamma Imaging Cherenkov Telescopes), applying a 3HSP source as observation seed. Moreover, with a dedicated gamma-ray analysis on the position of bright 3HSP sources using Fermi PASS8 data, we have found 150 new gamma-ray detections recently published in the 1BIGB catalog. To optimise the search for new blazars making full use of all available multi-frequency data we have developed a new software tool, called VOU-Blazars. The tool, based on Virtual Observatory (VO) protocols and developed within the Open Universe initiative, can identify blazars in relatively large regions of the sky, such as gamma-ray and neutrino uncertainty regions. % and rule out bad and uncertain candidates. %With VOU-Blazars, we will find more HSP candidates and figure out the counterpart for VHE sources in a more efficient way. Using radio and gamma-ray flux limited and largest ever subsamples of the 3HSP catalog we explored the statistical and evolution properties of HSP blazars, deriving the radio and gamma-ray LogN-LogS, luminosity function, as well as testing for the presence of cosmological evolution using the V/Vmax test. Our results confirm with unprecedented statistical robustness the presence of negative evolution. The luminosity function and LogN-LogS of HSP blazars imply that there is no preference for high nu peak sources in faint luminous/flux bins, contrary to the predictions of the ``blazar sequence''.