EXTENDED HOT-GAS HALOS AROUND STARBURST GALAXIES

A reanalysis of Einstein IPC data and new observations from the Ginga LAC indicate the presence of extended X-ray emission (10-50 kpc) aroun d the starburst galaxy M82. Here, we discuss our model of this emissio n, which was obtained by performing numerical hydrodynamic simulations of the starburst event to much later times and larger scales than wer e previously considered. For our models, we adopted a supernova rate o f 0.1 yr-1, and an extended low-density static halo that is bound to t he galaxy. There are three stages to the evolution of the wind-blown b ubble and the propagation of the shock front: the bubble expands in an almost uniform density disk gas, with a deceleration of the shock fro nt (t less than or similar to 3.6 Myr); breakout from the disk and the upward acceleration of the shock front (3.6 Myr less than or similar to t less than or similar to 18 Myr); propagation into the halo, leadi ng to a more spherical system and shock deceleration (18 Myr less than or similar to t). For a halo density of 10(-3) cm-3, the outflow reac hes a distance of 40-50 kpc from the center of the starburst galaxy in 50 Myr. We calculated the time evolution of the X-ray luminosity and found that the extended starburst emits 3 x 10(39) erg s-1 to 10(40) e rg s-1 in the Ginga LAC band and approximately 10(41) erg s-1 in the E instein or ROSAT HRI band. The degree of the ionization equilibrium in the outflow and its effect on the iron Kalpha line emission are discu ssed.