Sato, Shinji; Akimoto, Fumie; Furuzawa, Akihiro; Tawara, Yuzuru; Watanabe, Manabu; Kumai, Yasuki

Abstract

We have determined the mass profiles of dark halos in 83 objects observed by ASCA. The point-spread function of the X-ray telescope was deconvoled by the Richardson-Lucy algorithm, and the temperature profiles were calculated to obtain the mass profiles. The derived mass profiles are consistent with the Navarro, Frenk, & White model in (0.01-1.0)rvirial. We found a good correlation between the scale radius rs and the characteristic mass density δc, which indicates the self-similarity of dark halos. The spectrum index of primordial density fluctuation, P(k)~kn, was determined from the slope of the rs-δc relation. For M200=1012-1015 Msolar, our analysis gives n=-1.2+/-0.3 with a confidence level of 90%. The mass density of dark halos is a good indicator of the mean mass density of the universe at the time when the halos were assembled, z=zf. Assuming δc~(1+zf)3, we have determined the epoch when each dark halo was assembled. Our analysis indicates that the field elliptical galaxies and groups of galaxies formed approximately at 1+zf~=15 and at 1+zf~=7-10, respectively.