Detection of a temperature structure in the Coma cluster of galaxies with ASCA

Significant temperature variation is found from ASCA observations of the hot intracluster medium in the Coma cluster of galaxies. The whole cluster out to 1 degrees from the center was covered by 14 pointings. The temperature of the hot gas in the outside region is estimated by correcting for the stray-light effect from the bright center. The inferred temperature is lower than 4.5 keV in the west region and higher than 10 keV in the east, both offset by 40' (1.6 Mpc for H-0 = 50 km s(-1) Mpc(-1)) from the center. The temperature variation is not explained by a systematic error in the complex point-spread function of the ASCA X-ray telescope. The azimuthal variation of temperature is probably caused by recent mergers and may reflect an extended distribution of the dark matter.