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The 2009 Fermi Symposium

Fermi Large Area Telescope Detection of Steep Spectrum Radio Sources

Elizabetta Cavazzuti, ASI-ASDC Rome


Steep Spectrum Radio Sources (SSRS) are usually revealed by low-frequency radio surveys able to select objects primarily on the basis of the relatively steep spectrum synchrotron emission of their extended lobes (rather than cores, jets or hot spots). SSRS are considered elusive gamma targets. Their MeV-GeV emission is expected to be less amplified when compared to blazars, as the SSRS jets are seen at larger inclination angles. In spite of this, the Large Area Telescope (LAT) aboard the Fermi Gamma-Ray Telescope has allowed the detection of several SSRS (mainly Fanaroff & Riley type I Radio Galaxies) and the confirmation of the previous tentative EGRET detection of the Fanaroff & Riley type II Radio Galaxy 3C111. In this work, the radio and multiwavelength properties of LAT-detected SSRS and blazars are compared, and the possible differences/analogies discussed within the current jet emission model scenarios.