出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：We outline the main results of recent extensive multi-wavelength studies of radio, x-ray and g -ray selected blazars carried out through large observational campaigns involving several space and ground-based facilities, including the Planck, Swift, and Fermi satellites. All observed blazars exhibit the well-known double humped Spectral EnergyDistribution (SED), albeitwith significant differences in the position of the maxima and in their relative strength. The multi-band selection approach clearly demonstrated that selection effects play a major role in determining the observed properties of blazars. These biases cannot be ignored when drawing conclusions on the physical properties of blazars as a class. The average position of the synchrotron peak of FSRQs is located at approximately 1013 Hz in all samples, while that of BL Lacs is systematically shifted to higher frequencies, with a distribution that is strongly influenced by the selection method. The observed Compton dominance (CD) also largely depends on the way blazars are discovered, with g -ray selected FSRQs showing the largest CD values and radio selected objects exhibiting similar power in the synchrotron and inverse Compton components as the most frequent behavior. The multifrequency emission of most FSRQs is not consistent with simple homogeneous Synchrotron Self Compton (SSC) emission with an observed g -ray flux often in excess of that predicted by this simple model. However, a surprisingly large fraction (≈ 30-40%) of radio and X-ray selected blazars have not been detected as g -ray sources even integrating more than two years of Fermi- LAT data; the SED of these blazars is consistent with simple SSC models.
