Investigation of Obscured Flat Spectrum Radio AGN with the IceCube Neutrino Observatory
August 16, 2017
August 03, 2018
The IceCube Collaboration recently reported the first detection of high-energy extraterrestrial neutrinos. Nonetheless, their origins are still unknown. In view of the IceCube discovery, active galactic nuclei (AGN) and gamma-ray bursts (GRBs) have been explored as possible sources, but no significant neutrino flux from these objects has been observed yet. The AGN that have previously been investigated by IceCube are characterized by a large gamma-ray flux as observed by dedicated instruments like the Fermi Space Telescope. In these bright AGN, neutrinos are expected to be generated via charged pion decay, as counterparts of the $\gamma$-rays produced by the decay of neutral pions. In contrast to the previously studied objects, it is also possible to target a specific class of AGN that show weak emission at the highest frequencies. These so-called "Obscured Flat Spectrum Radio AGN" show indications for a radio jet pointing towards Earth, as well as a column of matter in our line of sight that blocks high-energy electromagnetic emission from the central engine of the source. In addition to the blocked electromagnetic emission, a possible hadronic component will also be blocked by the obscuring material. This hadron beam dump is expected to give rise to an additional neutrino flux. Here we present results of a search for neutrino emission from selected AGN of this type using IceCube data.
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