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Constraining non-thermal energy in galaxy clusters

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Franco Vazza

on 18 February 2017

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Transcript of Constraining non-thermal energy in galaxy clusters

Non-thermal energy in the ICM:
a gateway to cosmic rays, plasma physics & magnetogenesis

Where are the CR-protons?
Summary:
NT energy in clusters: small & linked to important physics
Turbulence in the ICM
Where are the CR-protons?
flat
radial profiles

allowed ~% level of ICM energy, as in Fermi+14.

mostly constrains accelerat. efficiency in cluster shocks (M<5)
A solution?

-
(radio) electrons

accelerated by
shock drift acceleration + DSA at ~perpendicular M<5 shocks
(Guo+15)

-
protons
accelerated only by
quasi-parall. shocks (Caprioli+14)
-> same results from semianalytical
models of
double relics

-> too large DSA efficiency required,
troubles with FERMI upper limits.
Radial distribution of CR/gas pressure ratio
ENZO simulations: PPM +
2 fluid models for Cosmic Rays
Vazza et al. 2012, 2013, 2014, 2016
~1/2-1/3 objects above FERMI (stacking) limits.

shock reacceleration of CRs
does not
help here.
Predicted emission vs observed FERMI limits
Radio relics & gamma
10 cluster with double relics.
CRe & B-field from radio.
CRp injection based on DSA.

-> comparison with FERMI
(stacking) limits.

-> constrain acceleration eff.



Using observed double relics to
predict gamma-ray emission:
Radio relics & gamma
(Vazza & Bruggen 2014 MNRAS)
(Vazza, Eckert et al. 2015 MNRAS)
Where are the CR protons?
~1/3 of clusters emits
above FERMI limits.
Simulated Gamma-Mass relations

cosmic rays gas density
~2 million CPU hours on CURIE@Genci, Prace project 2014
Obliquity & cosmic ray acceleration in the ICM
ENZO-MHD, 5 levels of AMR
Lagrangian tracers to simulate CRs
(Wittor, FV, Brüggen, submitted)
Franco Vazza (Hamburg University)
+M.Brüggen, T. Jones, D. Wittor, C. Gheller, D.Eckert, G. Brunetti, D. Ryu, A. Bonafede
The shocking and turbulent life of a galaxy cluster(1)
Heating
Cosmic rays
The shocking and turbulent life of a galaxy cluster(2)
Magnetic fields
Pressure support
Filtering & shocks
do matter.
Turbulence is always referred to a scale.
Turbulence in the ICM
New high-resolution simulations of galaxy clusters/groups
@Univ. Minnesota








total
velocity



small-scale
filtered
(<200kpc)
Turbulence in the ICM
Turbulence in the ICM
compressive modes solenoidal modes
-> particle acceleration -> dynamo amplification
Turbulent dissipation rate ~
Turbulence in the ICM
A minimal recap of ~robust previous findings
Cosmic rays in the ICM (1)
Cosmic rays protons from structure formation shocks predicted since long.
Pfrommer+07
Updates on the accel.efficiency in DSA following the inclusion of more physics (-> Kang's talk)
Efficiency for M<5 very uncertain

Where are the CR-protons?
Ackermann et al. 2014
no detection of hadronic emission after ~7 years of FERMI-LAT.

CR energy must be <% of E_thermal inside Rvir
-> test of acceleration
efficiency by cosmic shocks
thermal
(e.g. Berezkinsky+98, Volk+99, Miniati+2001, Gabici & Blasi 02, Pfrommer & Ensslin 04...)
~400 clusters M>10 Msol
V=300-50 Mpc , Dx =50-200 kpc
non-rad. vs cooling+AGN (
simplistic
)
several acceleration models
simulated stacking
Observer vs simulated hadronic emission

uniform
20 kpc res.

~200 timesteps/cluster

shock<-> vorticity

compressive<-> solenoidal
(Vazza, Jones, Bruggen, Brunetti, Gheller, Porter, Ryu sub.)
Turbulence in the ICM(2)
(Short recap on previous works)
(Vazza, Roediger & Bruggen 12)
(Vazza et al. 2011)
Velocity spectra ~ "Kolmogorov"
Turb.energy <10% in centre
Miniati 14

astrophysical origin
What is the origin of cosmic magnetism ?
primordial origin
VS
The Square Kilometer Array
galaxy formation
Donnert+08
seeding by AGN/SN:
Li+06, Dubois+07, Xu+08, Donnert+08, Beck+13...
AGN+SF
primordial
new ENZO simulations tailored for radio surveys
-> SKA
~30 million CPU hours on Piz-Daint @ CSCS
largest MHD simulations
to date 2400 cells / DM particles
ENZO AMR runs (6 levels) , PLM+ MHD (Dedner)
16 kpc resolution
primordial vs AGN seeding
-> models diverge significantly for >0.5 R200
Traces of magnetogenesis in cluster outskirts ?
Faraday Rotation
profiles diverge for >R500
Barely observable with JVLA.
Should be possible with
SKA-MID!
Vazza+06,09,10,11,12
(see also Dolag+05, Lau+07, Iapichino+08, Ryu+08, Gaspari+14, Schmidt+15)

velocity spectrum ~ Kolmogorov
turb. press. support increases outwards
turbulence increased during mergers
ICM2016-Minneapolis
DSA acceleration efficiency at weak shocks must be revised down by ~ 10
Traces of magnetogensis in cluster outskirts ?
Cluster centre:
solenoidal
turbulence ->
dynamo (see also Ryu+08, Cho+14)
Cluster outskirts:
compressive
motions ->
no dynamo(?), memory of seeds fields
~small-scale dynamo
Observables in cluster outskirts
Vazza, Bruggen, Wittor,
Gheller, Eckert & Stubbe
2016 MNRAS
Turbulence in the ICM
Terms ruling enstrophy evolution:
Continuum emission
possible with surveys at
low frequencies:
->LOFAR, MWA, SKA-LOW
ITASCA SIMULATED CLUSTER SAMPLE 2016, FV, Jones et al.
ITASCA SIMULATED CLUSTER SAMPLE 2016, FV, Jones et al.
Vazza et al., in prep.
FERMI limits constrain the shock
acceleration efficiency for M<5

Most of turbulent dissipation via solenoidal modes.
Vorticity more transported than generated.

Cluster outskirts
should keep the memory of magnetogenesis

t
~no dynamo
X-ray -> THERMAL energy
Radio emission + Faraday Rotation -> MAGNETIC energy ~1-2 % E_th
X-ray/SZ fluctuations
-> TURBULENT energy ~5% E_th
gamma-ray (non-detection)
-> CR energy <% E_th
Brown+Rudnick+10
Churazov+12
FERMI Collab.+15
Hydrostatic mass bias & cluster cosmology
THERM
Acceleration efficiency of shocks in the ICM
Latest on turbulence
in the ICM
Cluster magnetism & magnetogenesis
Non-thermal constraints from COMA:
This talk:
the total non-thermal energy is ~8%
Snowden+07
3D rendering by T. Jones & D.Porter
3D rendering by T. Jones & D.Porter
3D rendering by C-Gheller with SPLOTCH
Diffusive shock acceleration
13
Vazza, Bruggen, Wittor,
Gheller, Eckert & Stubbe
2016 MNRAS
this work
FV & Brüggen+14
FV,Eckert,Brüggen & Huber 2015
all obliquities only >50 shocks
o
ELECTRON acceleration & relics
-> emission is only ~50% reduced
PROTON acceleration & FERMI LIMITS
-> gamma-ray emission reduced by ~5
-> still larger than COMA limits
90-99% dissipation into solenoidal modes
compressive budget increases outwards
Stretching+advection dominant in merger shocks (i.e. relics)
Baroc.+compress. large in accr. shocks
cosmology
amplification of weak primoridal fields

(e.g. Dolag+99 , Ryu+08, Bruggen+05, Vazza+14.., Marinacci +15)
3
3
3
3
(FV et al, in prep.)
Red=temperature
Blue=magnetic field

Miniati+01
THANKS
see Vazza, Ferrari+15,16
Kinetic spectra
Magnetic spectra
Turbulence in the ICM
Solenoidal
modes dominate all scales
Compressive
modes sensitive to mergers
Velocity Power spectra Mode ratios
MERGER
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