Suzaku Observations of the Merging Cluster Abell 85: Temperature Map and Impact Direction
Abstract
To investigate the present situation of the merging in the southern outer region of Abell 85, we carried out long-time (∼100 ks) observations with Suzaku, and produced an X-ray hardness ratio map. We found a high hardness ratio peak on the east side of a subcluster located south of the cluster; an X-ray spectrum of the region including this peak indicates a high temperature of ∼8.5 keV. This hot spot has not been reported so far. We consider that this hot spot is a postshock region produced by the infall of the subcluster from the southwest. By using the Rankine-Hugoniot jump conditions for shocks, the Mach number and the infall velocity of the subcluster were obtained as 1.5±0.2 and 1950+290-280km s-1, respectively, in the case of merging with the subcluster from the southwest direction. By using the difference in redshift between A 85 and the subcluster obtained from optical observations, the angle between the line of sight and the direction of the motion of the subcluster is estimated to be 75°+7°-8°. We estimate the kinetic energy of the subcluster and the energy used for the intracluster medium (ICM) heating to be ∼1063 and lsim 8 × 1060erg, respectively. This shows that the deceleration of the subcluster by the ICM heating has been negligibly small.
- Publication:
-
Publications of the Astronomical Society of Japan
- Pub Date:
- June 2010
- DOI:
- 10.1093/pasj/62.3.743
- arXiv:
- arXiv:1006.4328
- Bibcode:
- 2010PASJ...62..743T
- Keywords:
-
- galaxies: clusters: individual (Abell 85);
- galaxies: intergalactic medium;
- shock waves;
- X-rays: galaxies: clusters;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 21 pages, 10 figure, accepted for publication in PASJ. Paper with high resolution figures is available at http://www.adc.nao.ac.jp/people/~ntanaka/Doc/article/A85_201006.pdf