IceCube has reported the detection of a diffuse TeV-PeV neutrino emission, for which the flat spectrum radio quasars （FSRQs） have been proposed to be the candidate sources. Here we assume that the neutrino flux from...IceCube has reported the detection of a diffuse TeV-PeV neutrino emission, for which the flat spectrum radio quasars （FSRQs） have been proposed to be the candidate sources. Here we assume that the neutrino flux from FSRQs is proportional to their gamma-ray ones, and obtain the gamma-ray/neutrino flux ratio by the diffuse gamma-ray flux from Fermi-LAT measurement of FSRQs and the diffuse neutrino flux detected by IceCube. We apply this ratio to individual FSRQs and hence predict their neutrino flux. We find that a large fraction of candidate FSRQs from the northern sky in the IceCube point source search has predicted neutrino flux above the IceCube upper limit; and for the sample of stacking search for neutrinos by IceCube, the predicted stacked flux is even larger than the upper limit of stacked flux by orders of magnitude. Therefore the IceCube limit from stacking searches, combined with the Fermi-LAT observations, already rejects FSRQs as the main sources of IceCube-detected diffuse neutrinos： FSRQs can only account for 〈 10% 〈 4%） of the IceCube-detected diffuse neutrino flux, according to the stacking searches from the whole （northern） sky. The derived small neutrino/gamma-ray flux ratio also implies that the gamma-ray emission from FSRQs cannot be produced by the secondary le^tons and photons from the Non nroduction nrocesses. The caveat in the assumntions is discussed.展开更多
基金The NSAF(Grant No.U1630246)the National Natural Science Foundation of China(Grants No.11575298,No.91230205,No.11575031,and No.11175026)+3 种基金the National Key Research and Development Program(No.2016YFA0401100)the National Science Challenging Programthe National Basic Research 973 Projects(No.2013CBA01500 and No.2013CB834100)the National High-Tech 863 Project
基金supported by the National Natural Science Foundation of China(Grant No.11273005)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20120001110064)the National Program on Key Basic Research Project(Grant No.2014CB845800)
文摘IceCube has reported the detection of a diffuse TeV-PeV neutrino emission, for which the flat spectrum radio quasars （FSRQs） have been proposed to be the candidate sources. Here we assume that the neutrino flux from FSRQs is proportional to their gamma-ray ones, and obtain the gamma-ray/neutrino flux ratio by the diffuse gamma-ray flux from Fermi-LAT measurement of FSRQs and the diffuse neutrino flux detected by IceCube. We apply this ratio to individual FSRQs and hence predict their neutrino flux. We find that a large fraction of candidate FSRQs from the northern sky in the IceCube point source search has predicted neutrino flux above the IceCube upper limit; and for the sample of stacking search for neutrinos by IceCube, the predicted stacked flux is even larger than the upper limit of stacked flux by orders of magnitude. Therefore the IceCube limit from stacking searches, combined with the Fermi-LAT observations, already rejects FSRQs as the main sources of IceCube-detected diffuse neutrinos： FSRQs can only account for 〈 10% 〈 4%） of the IceCube-detected diffuse neutrino flux, according to the stacking searches from the whole （northern） sky. The derived small neutrino/gamma-ray flux ratio also implies that the gamma-ray emission from FSRQs cannot be produced by the secondary le^tons and photons from the Non nroduction nrocesses. The caveat in the assumntions is discussed.
