Distribution of Si, Fe, and Ni in the Intracluster Medium of the Coma Cluster

作者：Matsushita Kyoko^*; Sato Takuya; Sakuma Eri; Sato Kosuke

来源：Publications of the Astronomical Society of Japan, 2013, 65(1): 10.

DOI：10.1093/pasj/65.1.10

• galaxies: clusters:individual (Abell 1656, the Coma cluster)
• X-rays: galaxies
• X-rays: intracluster medium

We studied the distributions of Si, Fe, and Ni in the intracluster medium (ICM) of the Coma cluster, one of the largest clusters in the nearby universe, using XMM-Newton data up to 0.5 r(180) and Suzaku data of the central region up to 0.16 r(180). Using the flux ratios of the Ly alpha line of H-like Si and the 7.8 keV line blend to the K alpha line of He-like Fe, the abundance ratios of Si to Fe and Ni to Fe of the ICM were derived using APEC model v2.0.1. The Si/Fe ratio in the ICM of the Coma cluster shows no radial gradient. The emission-weighted averages of the Si/Fe ratio in the ICM within 0.0-0.2r(180), 0.2-0.5r(180), and 0.0-0.5r(180) are 0.97 +/- 0.11, 1.05 +/- 0.36, and 0.99 +/- 0.13, respectively, in solar units using the solar abundance table by Lodders (2003, ApJ, 591, 1220). These values are close to those of smaller clusters and groups of galaxies. Using the Suzaku data of the central region, the derived Ni/Fe ratio of the ICM is 0.6-1.5 in solar units, according to the same solar abundance table. The systematic difference in the derived abundance ratios by different plasma codes are about 10%. Therefore, for the ICM in the Coma cluster, the abundance pattern of Si, Fe, and Ni is consistent with the same mixture of the yields of supernova (SN) II and SN Ia in our Galaxy. Within 0.5 r(180), the cumulative iron mass-to-light ratio increases with radius, and its radial profile is similar to those of relaxed smaller clusters with cD galaxies at their center. Using the observed Si/Fe ratio, the cumulative metal mass-to-light ratios at 0.5 r(180) are compared with theoretical expectations.

• 出版日期2013-2-25