The 1 Mpc giant head-tail radio galaxy IC 711: 3-dimensional simulation and additional constraints on the ram pressure theory

Abstract

Recent observations of the longest known head-tail galaxy IC 711, at long wavelengths have shown it to extend farther than previously known. At δ 74 cm, Vallee and Roger (1987) found it to stretch 17′ (930 kpc) behind the optical nucleus of this elliptical galaxy. At δ92 cm, Vallee and Strom (1988) found it to stretch 18.3′ (1 Mpc) behind the optical nucleus. What new physics can be learned from it? To that end, a theoretical simulation in 3 dimensions of the longest head-tail galaxy has been performed, building the radio trail cell by cell inside a volume of space composed of 8 million cells, with each cell being assigned a proper radio emissivity. Matching ram pressure theory and recent observations yields a primary fast decrease of the radio luminosity with time or distance from the optical nucleus of the galaxy, and a secondary periodic variation of the radio luminosity every 500 kpc. Near the end of the tail, a sudden and unpredicted flare-up of the observed width of the tail requires a sudden change in the jet's physical conditions about 2 Gyr earlier, or that of the surroundings.