γ-ray observations of extraterrestrial neutrino track events

Brown, Anthony M.; Adams, Jenni; Chadwick, Paula M.

Abstract

In this paper we report the results of a γ-ray study of IceCube's extraterrestrial neutrino candidates detected as track-like events. Using 70 months of Fermi-Large Area Telescope (LAT) observations, a likelihood analysis of all 1–300 GeV photons within 5° of the track-like neutrino candidates’ origin was undertaken, to search for spatially coincident γ-ray emission. One of IceCube's HESE (High Energy Starting Event) track events was found to be spatially coincident with a γ-ray bright active galactic nucleus (AGN), PKS 0723-008. We find however that the chance probability for Fermi-LAT detected AGN to be spatially coincident with a single HESE track-like event is high (∼37 per cent). We therefore find no evidence of γ-ray emission associated with the detection of IceCube's HESE track-like neutrino candidates. Upper limits were calculated in the energy range of 1–300 GeV, assuming a point source origin for the neutrino events considered. The implications for the non-detection of γ-ray emission from the source of the HESE track-like events are briefly discussed. The large time period analysed in our study did however reveal two new γ-ray point sources. With a flux of (1.28 ± 0.08) × 10−9 photons cm−2 s−1, in the 1–300 GeV energy range, and an associated TS value of 220.6, one of these new point sources is positionally coincident with the AGN PKS 1346-112. The other point source has a 1–300 GeV flux of (7.95 ± 1.23) × 10−10 photons cm−2 s−1 and an associated TS value of 92.4. This new point source is spatially coincident with the radio source NVSS J072534 + 021645 suggesting that it too is an AGN.

Citation

Brown, A. M., Adams, J., & Chadwick, P. M. (2015). γ-ray observations of extraterrestrial neutrino track events. Monthly Notices of the Royal Astronomical Society, 451(1), 323-331. https://doi.org/10.1093/mnras/stv899

• Journal Article Type: Article
• Acceptance Date: Apr 21, 2015
• Publication Date: Jul 21, 2015
• Deposit Date: May 29, 2015
• Publicly Available Date: Jun 29, 2015
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 451
• Issue: 1
• Pages: 323-331
• DOI: https://doi.org/10.1093/mnras/stv899
• Keywords: Neutrinos, Galaxies: active, Gamma rays: galaxies, Gamma-rays: general.
• Public URL: https://durham-repository.worktribe.com/output/1437017