ASCA observations of groups at radii of low overdensity: Implications for the cosmic preheating

摘要: Through a three-dimensional modeling of ASCA observations, we performed spatially resolved X-ray spectroscopic study, extending to radii exceeding 150 kpc, for sample nine groups galaxies. Combined with published ROSAT results, conclude that these systems generally exhibit strong temperature decline at outer radii. In our best case, NGC 3268, this corresponds flattening the entropy profile level ~400 keV cm2. This value is high compared both observed floor ~100 cm2 and expected from gravitational heating. We suggest in most densities 500 times critical driven purely by nongravitational heating processes. After comparison larger clusters, there variation between within every system. Using models cluster formation as reference frame, established accreted gas reaches an 400 redshift 2.0-2.5, while such entropies where not present redshifts higher than 2.8-3.5, favoring nearly instantaneous preheating. Adopting galactic winds source preheating scaling released energy metal abundance, could be ascribed mostly typical overdensity injection, ~30 100 ~5