X-ray Surface Brightness Profiles of
Galaxy Groups from Cosmological
Simulations
RUDRANI KAR CHOWDHURY
PRESIDENCY UNIVERSITY
M.Sc thesis advisor
Suchetana Chatterjee
Lx – T Relation in Galaxy Groups/Clusters
Analytic models and numerical simulations of
cluster formation predict that temperature and Xray luminosity are related as
LX  T
2
but observation shows that
LX  T
3
2.98 0.19 for 0.069<Z<0.2
(red circles)
2.62  0.21 for Z>0.2
(green triangles)
2.69  0.18 for cooling
clusters (blue squares)
Andersson et. al 2009
Some other effect seems to be responsible for changing the
LX-T slope. One possibility is AGN Feedback
ACTIVE GALACTIC NUCLEI (AGN)
CENTRAL SUPERMASSIVE BLACK HOLE
IN A GALAXY ACCRETING MASS FROM
THE SURROUNDINGS
AGN FEEDBACK IN GALAXY CLUSTERS
HST image of MS0735.6 + 7421 cluster
Chandra X-ray image in blue
VLA radio image in red
McNamara & Nulsen 2007
OTHER OBSERVATIONAL PROOF OF
AGN ACTIVITY
Cooling flow problem in galaxy clusters
 Cosmic downsizing
Aim of this Work
Using two cosmological hydrodynamic
simulation we now want to study the effect of
feedback on the X-ray surface brightness profile
of galaxy groups.
Both simulation starts from the same initial
conditions.
One set includes a model of AGN feedback
One set does not include AGN feedback.
COSMOLOGICAL SIMULATION
The simulation used in this purpose has the
following properties….
 Box size 34 Mpc
 Total no. of particles in the box 2  216 3
 Total no. of particles is the sum of cold dark matter
particles gas particles, star particles and black hole
particles.
 Mass of dark matter is 2 .75  10 8 h  1 M 
 Mass of gas particles is 4 .24  10 7 h  1 M 
Simulation Snapshot
DiMatteo et al. 2008
Density of gas color coded by temperature.
Yellow circles represent black holes.
Dark matter and stars are not shown in this plot.
BLACK HOLE FEEDBACK
 Seed black hole grow in size by
accreting mass from the surrounding
 Accretion rate is given by

M  4  ( G M  ) /( c  v )
2
2
2
2 3/2
 Luminosity of theblack hole is
2
Lr   M C
 Feedback energy is

E   f Lr
METHODOLOGY
 Spherical region of radius 100 kpc is considered around
the black hole
 X-ray map is constructed by allocating spatial grids to the
region of space and computing smoothed x-ray flux at a
given grid point
 To construct the x-ray surface brightness profile , map is
divided into a no. of annular regions and x-ray flux of each
region is calculated and a differential profile of flux is made
as a function of distance
Mass of 2nd most massive BH at Z=3 is 7 .15  10 8 h 1 M 
 Accretion rate is 0 . 240 M  / year
Mass of the host halo of this black hole 4 . 71  10 13 M 
RESULT
The left panel shows the X-ray map with feedback for 2nd most massive
black hole at Z=3. The right panel shows the x-ray map without feedback
for the same black hole
This is the differential profile of x-ray flux for with (dotted
line) feedback and without feedback (solid line) cases
Conclusion and Future Work
 Without AGN feedback the x-ray flux
is high at the centre
 X-ray flux is low at the centre & high
outside when AGN activity is considered
 Our result is in accordance with the
observation by McNamara & Nulsen
 We have studied this AGN activity for
one red shift & one black hole
 In future our plan is to study this
effect for more than one red shift &
black hole
THANK YOU