Seeking Neutrino Emission from AGN through Temporal and Spatial Cross Correlation

TL;DR

This study assesses the potential of upcoming astronomical and neutrino observatories to detect correlations between active galactic nuclei (AGN) emissions and high-energy astrophysical neutrinos, aiming to identify AGN as neutrino sources.

Contribution

It introduces a method combining spatial and temporal cross-correlation analyses to evaluate AGN contributions to neutrino flux using future observational data.

Findings

Potential to detect ~10% AGN contribution to neutrino flux at 3σ significance.

Spatial correlations provide the strongest evidence for AGN-neutrino link.

Temporal correlations may help identify variability patterns associated with neutrino emission.

Abstract

Active galactic nuclei (AGN) are a promising source for high-energy astrophysical neutrinos (HEANs). By the end of 2022, the Vera C. Rubin Observatory (VRO) will begin to observe $\gtrsim10$ million AGN with a regular and high cadence. Here, we evaluate the capacity of VRO, in tandem with various current and upcoming neutrino telescopes, to establish AGN as HEAN emitters. To do so, we assume that the neutrino luminosity from any given AGN at any given time is proportional to the electromagnetic luminosity. We then estimate the error with which this fraction can be measured through spatial and temporal cross-correlation of VRO light curves with IceCube, KM3NeT, and Bakail-GVD. We find that it may be possible to detect AGN contributions at the $\sim3 \sigma$ level to the HEAN flux even if these AGN contribute only $\sim10\%$ of the HEAN flux. The bulk of this information comes from spatial correlations, although the temporal information improves the sensitivity a bit. The results also imply that if an angular correlation is detected with high signal-to-noise, there may be prospects to detect a correlation between AGN variability and neutrino arrival times. The small HEAN fraction estimated here to be accessible to the entirety of the VRO AGN sample suggests that valuable information on the character of the emitting AGN may be obtained through similar analyses on different sub-populations of AGN.