TIME-INTEGRATED SEARCHES FOR POINT-LIKE SOURCES OF NEUTRINOS WITH THE 40-STRING IceCube DETECTOR

Abstract

We present the results of time-integrated searches for astrophysical neutrino\nsources in both the northern and southern skies. Data were collected using the\npartially-completed IceCube detector in the 40-string configuration between\n2008 April 5 and 2009 May 20, totaling 375.5 days livetime. An unbinned maximum\nlikelihood ratio method is used to search for astrophysical signals. The data\nsample contains 36,900 events: 14,121 from the northern sky, mostly muons\ninduced by atmospheric neutrinos and 22,779 from the southern sky, mostly high\nenergy atmospheric muons. The analysis includes searches for individual point\nsources and targeted searches for specific stacked source classes and spatially\nextended sources. While this analysis is sensitive to TeV-PeV energy neutrinos\nin the northern sky, it is primarily sensitive to neutrinos with energy greater\nthan about 1 PeV in the southern sky. No evidence for a signal is found in any\nof the searches. Limits are set for neutrino fluxes from astrophysical sources\nover the entire sky and compared to predictions. The sensitivity is at least a\nfactor of two better than previous searches (depending on declination), with\n90% confidence level muon neutrino flux upper limits being between E^2 dN/dE ~\n2 - 200 \\times 10^-12 TeV cm^-2 s^-1 in the northern sky and between 3 -700\n\\times 10^-12 TeV cm^-2 s^-1 in the southern sky. The stacked source searches\nprovide the best limits to specific source classes. The full IceCube detector\nis expected to improve the sensitivity to E^-2 sources by another factor of two\nin the first year of operation.\n