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

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

SLIDE 1

G. A. Ogrean, M. Brüggen, R. van Weeren, H. Röttgering,
A. Simionescu, M. Hoeft and J. H. Croston

Multiple density discontinuities in the merging galaxy cluster CIZA J2242.8+5301

(1)CHEmical Evolution Rgs Sample

MNRAS 440, 3416-3425 (2014)

2014MNRAS.440.3416O

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SAUSAGE CLUSTER : GENERAL INFO

Correspondence between radio relics

and shock fronts ?

z = 0.19
1 arcmin = 192 kpc
L0.1-2.4 keV = 6.8 x 1044 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

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

Map : 1.4 GHz. Contours : ROSAT. (van Weeren et al. 2010)

SLIDE 3

CHANDRA IMAGE

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

SLIDE 4

BACKGROUND AND SECTORS

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

SLIDE 5

DISCONTINUITIES

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

?

M = 1.31+0.12-0.09

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

M = 1.43+0.09-0.08

DISCONTINUITIES

SLIDE 7

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

M = 1.25+0.07-0.06

?

DISCONTINUITIES

SLIDE 8

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

M = 1.26+0.08-0.07

DISCONTINUITIES

SLIDE 9

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

DETAILED RESULTS

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

DISCONTINUITIES

SLIDE 11

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

M = 1.27±0.03

DISCONTINUITIES

SLIDE 12

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

SUZAKU RESULTS

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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!

SLIDE 14

Mach number varies across the shock front ?
+ Synchrotron emission more sensitive to high Mach number

shocks ?

Additional contribution of re-accelerated CRs ?
Projection effects ?
Underestimation of post-shock temperature ?
Oblique (rather than parallel) shocks ?

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 ?

MX = 2.54+0.64-0.43 Mrad = 4.6+1.3-0.9

SLIDE 15

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

2) Nature of the inner density discontinuities ?

SLIDE 16

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 !

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 3) Sequential shocks ?

Violent relaxation of DM halos ?