Limits to the Intergalactic Magnetic Field from extended gamma-ray emission around blazars

M. FERNANDEZ ALONSO, VERITAS COLLABORATION: A.C. ROVERO

San Juan

Congreso; 59 Reunión Anual de la Asociación Argentina de Astronomía; 2016

ICATE

Intergalactic space is believed to contain non-zero magnetic fields (the Intergalactic Magnetic Field: IGMF) at scales of Mpc (the coherence length). To the date there is no direct detection/evidence of the IGMFand we have no certain information about its intensity and spatial properties. Very high energy (>100 GeV) gamma rays coming from blazars can produce electromagnetic cascades in the intergalactic medium. The spatial development of the charged component of these cascades is presumably affected by the IGMF which may produce a broadening of the emission beam, depending on the intensity and spatial distribution of this field. In this work we use VERITAS gamma ray observations of the blazar 1ES1218+304 and combine its angular (θ^2 ) distribution with intergalactic cascade simulations to calculate limits to the extended component emission (cascade fraction). Finally, we calculate an expected dependence of the cascade component with the intensity of the IGMF and compare it to predictions from simulations to derive limits. A preliminary analysis suggests an exclusion region for the intensity of a 1 Mpc (coherence length) IGMF between 5.62×10^−15 G and 3.16×10^−14 G.