Multiple density discontinuities in the merging galaxy cluster CIZA - PowerPoint PPT Presentation

MNRAS 440, 3416-3425 (2014) Multiple density discontinuities in the merging galaxy cluster CIZA J2242.8+5301 G. A. Ogrean, M. Brüggen, R. van Weeren, H. Röttgering, A. Simionescu, M. Hoeft and J. H. Croston 2014MNRAS.440.3416O (1) CHEmical Evolution Rgs Sample

SAUSAGE CLUSTER : GENERAL INFO • Correspondence between radio relics and shock fronts ? • z = 0.19 • 1 arcmin = 192 kpc • L 0.1-2.4 keV = 6.8 x 10 44 erg/s • Radio Mach number (DSA) = 4.6 +1.3-0.9 • X-ray Mach number = 3.15 ±0.52 +0.40-1.20 • Here : Chandra 200 ks observation + archival Suzaku observations Map : 1.4 GHz. Contours : ROSAT. (van Weeren et al. 2010) François Mernier Density discontinuities in the Sausage Cluster through X-rays (Ogrean et al. 2014) 2

CHANDRA IMAGE François Mernier Density discontinuities in the Sausage Cluster through X-rays (Ogrean et al. 2014) 2

BACKGROUND AND SECTORS François Mernier Density discontinuities in the Sausage Cluster through X-rays (Ogrean et al. 2014) 2

DISCONTINUITIES ? S1 M = 1.31 +0.12-0.09 François Mernier Density discontinuities in the Sausage Cluster through X-rays (Ogrean et al. 2014) 2

DISCONTINUITIES S2 M = 1.43 +0.09-0.08 François Mernier Density discontinuities in the Sausage Cluster through X-rays (Ogrean et al. 2014) 2

DISCONTINUITIES ? S3 M = 1.25 +0.07-0.06 François Mernier Density discontinuities in the Sausage Cluster through X-rays (Ogrean et al. 2014) 2

DISCONTINUITIES S4 M = 1.26 +0.08-0.07 François Mernier Density discontinuities in the Sausage Cluster through X-rays (Ogrean et al. 2014) 2

DETAILED RESULTS François Mernier Density discontinuities in the Sausage Cluster through X-rays (Ogrean et al. 2014) 2

DISCONTINUITIES François Mernier Density discontinuities in the Sausage Cluster through X-rays (Ogrean et al. 2014) 2

DISCONTINUITIES M = 1.27±0.03 François Mernier Density discontinuities in the Sausage Cluster through X-rays (Ogrean et al. 2014) 2

SUZAKU RESULTS François Mernier Density discontinuities in the Sausage Cluster through X-rays (Ogrean et al. 2014) 2

SUZAKU RESULTS No significant temperature drop in the inner shock fronts! François Mernier Density discontinuities in the Sausage Cluster through X-rays (Ogrean et al. 2014) 2

DISCUSSION 1) Comparison radio-predicted Mach number and X-ray predicted Mach number ? • Mach number varies across the shock front ? • + Synchrotron emission more sensitive to high Mach number shocks ? • Additional contribution of re-accelerated CRs ? • Projection effects ? M X = 2.54 +0.64-0.43 • Underestimation of post-shock temperature ? M rad = 4.6 +1.3-0.9 • Oblique (rather than parallel) shocks ? François Mernier Density discontinuities in the Sausage Cluster through X-rays (Ogrean et al. 2014) 2

DISCUSSION 2) Nature of the inner density discontinuities ? • Large distance + high temperature ➔ unlikely a cold front • Shock front ? Never seen without temperature jump... • ??? • ➔ more precise temperature measurements ? François Mernier Density discontinuities in the Sausage Cluster through X-rays (Ogrean et al. 2014) 2

DISCUSSION 3) No radio emission at the inner density discontinuities • Comparable to Abell 2146 (in case of shock front)... • ...but shocks not only on the merger axis ! • Diffusive Shock Acceleration : M=1.3 ➔ index ~ 4 • Radio relics might require pre-existing CR population ! 3) Sequential shocks ? • Violent relaxation of DM halos ? François Mernier Density discontinuities in the Sausage Cluster through X-rays (Ogrean et al. 2014) 2