Search for time-independent neutrino emission from astrophysical sources with 3 years of IceCube data

TL;DR

This study searched for astrophysical neutrino sources using three years of IceCube data, finding no significant signals but setting upper limits on neutrino fluxes and improving sensitivity over previous results.

Contribution

The paper presents the first comprehensive all-sky and targeted searches for neutrino point sources with three years of IceCube data, utilizing improved event selection and analysis techniques.

Findings

No significant neutrino point sources detected.

Upper limits set on neutrino fluxes between 0.9 and 23.2×10^{-12} TeV^{-1} cm^{-2} s^{-1}.

Sensitivity improved by a factor of 3.5 compared to previous analyses.

Abstract

We present the results of a search for neutrino point sources using the IceCube data collected between April 2008 and May 2011 with three partially completed configurations of the detector: the 40-, 59- and 79-string configurations. The live-time of this data set are 1,040 days. An unbinned maximum likelihood ratio test was used to search for an excess of neutrinos above the atmospheric background at any given direction in the sky. By adding two more years of data with improved event selection and reconstruction techniques, the sensitivity was improved by a factor 3.5 or more with respect to the previously published results obtained with the 40-string configuration of IceCube. We performed an all-sky survey and a dedicated search using a catalog of \textit{a priori} selected objects observed by other telescopes. In both searches, the data are compatible with the background-only hypothesis. In the absence of evidence for a signal, we set upper limits on the flux of muon neutrinos. For an E$^{-2}$ neutrino spectrum, the observed limits are between 0.9 and $23.2\times 10^{-12}$ TeV$^{-1}$ cm$^{-2}$s$^{-1}$. We also report upper limits for neutrino emission from groups of sources which were selected according to theoretical models or observational parameters and analysed with a stacking approach.