Search for CP Violating Signature of Intergalactic Magnetic Helicity in the Gamma Ray Sky

Understand

The existence of a cosmological magnetic field could be revealed by the effects of non-trivial helicity on large scales.

• We evaluate a CP odd statistic, $Q$, using gamma ray data obtained from Fermi satellite observations at high galactic latitudes to search for such a signature.
• Observed values of $Q$ are found to be non-zero; the probability of a similar signal in Monte Carlo simulations is $\sim 0.2\%$.
• Contamination from the Milky Way does not seem to be responsible for the signal since it is present even for data at very high galactic latitudes.