Hot Halo Gas in Galaxy Mergers

摘要

We report on the results of high-resolution hydrodynamic simulations of colliding galax-ies with hot halo gas. We find that : (i) A strong shock is produced in the galaxy halos before the first passage, increasing the temperature of the gas by almost an order of magnitude to ~10~(6.3) K. (ii) The X-ray luminosity of the shock is strongly dependent on the gas fraction. It is ≥ 10~(39)erg/s for gas fractions larger than 10%. (iii) The hot diffuse gas in the simulation also produces X-ray luminosities as large as 10~(42) erg/s.. This contributes to the total X-ray background in the Universe. (iv)~ 10-20% of the initial gas mass is unbound from the galaxies for equal-mass mergers. We use an analytical halo merger tree and estimate that. ≥ 10% of the total baryon content of the Universe could have been unbound via mergers over the history of the Universe.