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X-ray cavities in galaxy clusters. Myriam Gitti (UniBO,INAF-OABo). Collaborators: - Brian McNamara (Waterloo University & Ohio University) - Paul Nulsen (Harvard-Smithsonian Center for Astrophysics).  Arcetri, 7 Maggio 2009 . Plan of the talk Introduction galaxy clusters

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slide1

X-ray cavities in galaxy clusters

Myriam Gitti

(UniBO,INAF-OABo)

Collaborators: -Brian McNamara(Waterloo University & Ohio University)

-Paul Nulsen(Harvard-Smithsonian Center for Astrophysics)

 Arcetri, 7 Maggio 2009 

slide2

Plan of the talk

  • Introduction
        • galaxy clusters
        • X-ray properties of the intracluster medium (ICM)
        • “cooling flow” (CF) and “cooling flow problem”
  • X-ray cavities and radio bubbles
        • AGN/ICM interaction, heating of CF
  • MS0735: the most powerful AGN outburst
        • XMM data analysis and results
        • do (super-)cavities affect the average cluster properties?
slide4

Galaxy clusters

X-ray

visual

100 kpc

  • 100-1000 galaxies + intracluster medium (ICM) + dark matter (DM)
  • total mass ~ 1014 - 1015 M
  • size ~ some Mpc
slide5

Why do we study galaxy clusters?

Millennium Run

(Springel et al. 2005)

 Galaxy clusters are key objects for cosmological studies

  • structure formation (standard CDM scenario)
  • gravitational collapse of the dark matter
  • baryon specific physics
slide6

Galaxy Clusters (total mass)

~2%

~13%

~85%

dark

matter

galaxies

ICM

relativistic

particles

AGN radio loud

thermal plasma

magnetic fields

Optical emission

X-ray emission

Radio emission

Radio emission

slide7

Galaxy Clusters (total mass)

~2%

~13%

The ICM is a hot, optically thin plasma enriched in heavy elements

It emits in X-rays by thermal bemsstrahlung + lines

Jbr  Z2 neniT-1/2 e–h/kT

galaxies

ICM

AGN radio loud

thermal plasma

Radio emission

X-ray emission

slide8

ICMtemperature~ 0.5–15 keV

  • ICMdensity~ 10-4 -10-2cm-3
  • ICMmetallicity~ 0.3 solar
  • Luminosity ~ 1043-1046 ergs/s

Extracting ICM physical info from X-rays

  • temperature: from the position of the exponential cut-off in the spectrum
  • density: from the normalization of the spectrum int(ne2 dV)
  • metallicity: from lines of heavy elements (e.g., Iron K line complex at ~ 6.7 keV)
slide9

Modern X-ray Observatories

X-ray photons collected and focused by grazing incidence telescopes

CCD cameras: measurement of position and energy of incoming photon

Scheme of the two XMM telescopes equipped with EPIC-MOS and RGS. In the third, all the light is collected by EPIC-pn.

  • Chandraextremely good spatial resolution (~0.5’’)
  • XMM-Newtonexceptional collecting area and thus sensitivity,

three telescopes, large field of view (30’  30’)

slide10

ICM density distribution:

ICM(r) = ICM,0 [ 1+ (r/rcore)2 ]-3/2

cooling timetcool :characteristic time of energy radiated in X-rays

cooling radiusrcool: radius at which tcool= age of the cluster»H0-1

 Surface brightness profile:

S(r) = S0 [ 1+ (r/rcore)2 ]1/2-3

Within rcool, tcool<H0-1the cooling gas flows inward -with a

mass inflow rateM -and is compressed

hydrostatic eq.

ratio of energy per unit mass in galaxies to that in gas

kT

=2

 2/3

mH

Compression density increases  X-ray emissivityincreases

-model

CF cluster

non-CF cluster

CF cluster

non-CF cluster

(Cavaliere & Fusco Femiano 1976)

Cooling Flow (CF)– standard model

slide11

CF– observations

  • short cooling time
  • high density
  • low temperature
  • H filaments
  • OVI
  • molecular gas

 evidence of cooling

slide12

CF– observations

Lack of very cold gas

XMM/RGS does not see emission lines of gas at intermediate T (Fe XVII, OVII)

Gas drops toTmin~0.3 Tvir

Chandra spectra consistent

M(<Tmin)~(0.1-0.2)MX

 CF problem: why, and how, is the cooling of gas below Tvir/3 suppressed?

slide13

Signature of cooling below 2 keV suppressed

- absorption

-mixing

-inhomogeneous

metallicity

missing soft LX ~ LUV

- central AGN

- thermal conduction

- subcluster merging

- combinations/other...

  • Heating to balance cooling

M ~0.1MX

CF problem - possible solutions

slide15

Perseus

A2052

RBS797

3C317 – A2052

Fabian et al. 2000

Blanton et al. 2001

Gitti et al. 2006

AGN / ICM interaction

  • most CF clusters contain powerful radio sources associated withcD
  • central ICM shows “holes” often coincident with radio lobes (Chandra)

the radio“bubbles”displace the ICM, creating X-ray“cavities”

slide16

heating

 dissipation of

cavity enthalpy

the kinetic energy created in the wake of the rising cavity is equal to the enthalpy lost by the cavity as it rises

slide17

Cavity energy

direct measure of the total energy of AGN outburst

  • Study of radiosource properties

 ratio is insignificant

 age of radio-filled cavities assumpti

jet synchrotron power

r

t = r/v

total AGN power

(Birzan et al. 2004)

the kinetic energy created in the wake of the rising cavity is equal to the enthalpy lost by the cavity as it rises

slide18

Cavity properties

  • diameter  20-200 kpc
  • pV = 1055-1061 erg
  • ages = 107-108 yr
  • P = 1041-1046 erg/s

trend:feedback

(Birzan et al. 2004)

quenching of CFs

(Rafferty et al. 2006)

slide19

cooling and accretion onto a central BH

Cooling Flow

AGN outburst

cooling is reestablished

cooling is arrested

system settles down

Self-regulated feedback loop

slide20

The most powerful AGN outburst

Supercavities (~100s kpc) found inMS0735+7421, Hercules A, and Hydra A

McNamara & Nulsen

ARA&A 2007

AGN injects >1061 erg into the ICM  heating up to cluster-wide scale

slide21

L T2.6

L-T relation

Luminosity function

of Galaxies

L T2 gravity

(Benson et al. 2003)

(Markevitch 1998)

Problems addressed

  • substantial contribution to the pre-heating problem ?
  • common solution to CF problem and galaxy formation ?
  • what gives support to the cavities ?
  • do cavities affect the general cluster properties ?
ms0735
MS0735

MS0735+7421:

the most powerful AGN outburst as seen by XMM

slide23

1‘ = 210 kpc

H0 = 70 km/s/Mpc

M = 1- = 0.3

z = 0.216LX (2-10keV)~ 4.6 x 1044erg/s

Cavities

slide24

deficit of emission in the Nsector

Surface brightness profile

N sector

undisturbed cluster

60-180 kpc

Undisturbed

slide25

strong excess in the centre when compared to the model

Fit with a -model

Single -model not a good description of entire profile

fit

Fit to outer region:

 rcore = 195 kpc  = 0.77

Undisturbed

slide26

r

line of sight

Obs. spectrum (r) = spectra in shells

 deprojection analysis

Temperature profile

slide27

r

line of sight

Obs. spectrum (r) = spectra in shells

 deprojection analysis

Density profile

slide28

d P

G M(<r)

= - 

d r

r 2

d lnne

d lnT

-kTr

Mtot(<r) =

+

Gmp

d lnr

d lnr

Mass profile

Eq. hydrostatic equilibrium:  P = -....

assumption of spherical symmetry

 Total gravitational mass Mtot(<r) :

ne(r)

from -model or deprojection

slide29

kr2

3rT

dT

Mtot(<r) =

Gmp

r2+rc2

dr

Mass profile: from -model

Mass from beta

From T(r) & ne(r)

Total gravitational mass M(r)

assumption of spherical symmetry

assumption of hydrostatic eq.

if density follows -model:

ne(r) = ne,0 [ 1+ (r/rc)2 ]-3/2

slide30

1

r2

dP

Mtot(<r) =

G

nemp

dr

Mass profile: from deprojection

From T(r) & ne(r)

Total gravitational mass M(r)

assumption of spherical symmetry

assumption of hydrostatic eq.

if density and pressure are measured from deprojection analysis

slide31

Chandra + VLA (McNamara et al. 2005)

cavity N

indication of

13 KeV component

BUT

poor photon statistics does not allow us to claim a detection

What fills the cavities?

Radio lobes  relativistic electrons

Pext  10 Pradio,eq

 also hot, dilute thermal plasma?

slide32

shock front

pre-shocked gas

shock front

post-shocked gas

~ 10% temperature rise expected by shock model

Mach number M 1.4

XMM data consistent with T jump across the shock, but not definitive

Shock front

discussion
Discussion

MS0735+7421:

do (super-)cavities affect the average properties of galaxy clusters?

slide34

3 Hz2

3 Mtot(<r)

where c,z=

Overdensity=

8 G

4 c,z r3

r

(kpc)

Mtot,

(1014 M)

fgas,

(Mgas/Mtot)

200

2230

 650

15.6

 8.78

0.11

 0.06

virial radius rvirr200

2500

465

 160

1.77

 0.82

0.16

 0.08

Determination of r200 and r2500

we assume Mtot = MDM  fit with NFW profile (Navarro et al. 1996)...............................................to extrapolate M(r)

slide35

r2500 = 465 kpc

T2500 = 5.2 keV

MS0735

Scaled temperature profile (=2500)

6 relaxed clusters observed with Chandra

T2500 = 5.5 - 16 keV

(Allen et al. 2001)

slide36

MS0735

r2500 = 465 kpc

<TX>= 4.7 keV

Scaled temperature profile (=2500)

  • Clusters with supercavities: 3/30 (Rafferty et al. 2006) age ~ 108 yr
  • Outbursts active most of the time (Dunn et al. 2005)

 as NO marked effect is observed, large outbursts are likely occurring ~10% of the time in a signficant fraction of all CF clusters

12 relaxed clusters observed with Chandra

<TX> = 1.6 – 8.9 keV

(Vikhlinin et al. 2004)

slide37

MS0735

Scaled metallicity profile (=180)

9 CF clusters observed with BeppoSAX

H0 = 50 km/s/Mpc

=1, =0

(De Grandi & Molendi 2001)

slide38

LT2.6

Excess Entropy, “preheating” 1-3 kev/particle (Wu et al. 2000)

1. early star formation ?

2. AGN (early / late) ?

LT2gravity

(Markevitch 1998)

Luminosity vs. Temperature

 General L-T effect:

Steepening of L-T relation

MS0735: Mass within 1 Mpc is being heated at the level of 1/4 keV/particle

slide39

MS0735

CF and cavities:

1. cool gas lifted by outburst

2. compression in the shells

* WARNING! *

Bias for flux-limited surveys

Luminosity vs. Temperature

 Anomalous L-T effect:

MS0735 factor ~2 more luminous than expected from its temperature

(Markevitch 1998)

slide40

Rin

in

depends on cavity radius & shell thickness

 25 % for MS0735

Cavity expansion

ICM compression in shells

L L’

L

LX boost by cavities

slide41

“cavity effect”  25 %

* WARNING! * Overestimate fgas

Luminosity vs. Temperature

slide42

MS0735

(Voigt & Fabian 2006)

CMB :

 b/ m=0.1750.023

MS0735:

fgas,2500=0.1650.040

fgas,2500=0.1170.002

Allen et al. 2004 :

fgas,2500=0.0910.002

Vikhlinin et al. 2005 :

Gas mass fraction

r/r2500

conclusions
Conclusions
  • substantial contribution to the pre-heating problem ?

yes,  1/4 - 1/3 keV per particlepossible (feedback)

  • what gives support to the cavities ?

indications for a hot thermal component

  • do cavities affect the general cluster properties ?

not strongly

yes,  1/4 - 1/2 keV per particle

indication of a hot thermal component

T & Z profiles not strongly ; LX&fgas possibly

Gitti et al. 2007, ApJ, 660, 1118

slide44

…in the future…

  • search for lines at levels of observed star formation rates

XMM-RGS observations

  • calibration of radio synchrotron efficiency

(low frequency) radio observations probe the history of feedback and heating

  • models for the fueling and triggering of AGN outbursts

jet formation, dynamics, energetics, content, and radiative efficiency

  • “microphysics” of feedback process

how cavity enthalpy is dissipated? efficiency of heating? where is heat deposited?

  • determine AGN heating rate and contribution of AGN

outbursts to expected cluster scaling relations

large, unbiased search for cavities in a flux- or volume-limited sample

energetics
Energetics

SMBH Energy Output

Milky Way1) 1

M87 100,000

Perseus Cluster 10,000,000

Hydra A Cluster 100,000,000

MS0735+7421 1,000,000,000

1) Milky Way = 1051 erg in 100 Myr

slide48
data

Observation and data preparation

  • MS0735 observed by XMM-Newton in April 2005 for ~70 ks.
  • MOS1, MOS2, pn detectors in Full Frame Mode
  • Data analysis performed with SASv6.5.0
  • Exposure time after data cleaning (flares, etc.)  ~ 50 ks
  • Masked point sources
  • Vignetting correction with task evigweight (weighted method by Arnaud et al. 2001 )
  • Background from blank-sky observations (Lumb et al. 2002)
metallicity
Metallicity

Metallicity profile

Projected

Deprojected

cf analysis
CF analysis

Parameter

1 isothcomp. (MEKAL)

2 isot comp.

(MEKAL+MEKAL)

kT (keV)

3.9(+0.1/-0.1)

6.1(+1.3/-0.6)

CF

(MEKAL+MKCFLOW)

M (M/yr)

-

0.73 Norm

7.6(+0.5/-1.3)

2.3(+0.4/-0.4)

kTlow(keV)

-

260(+30/-20)

Normlow

839/785

2/ dof

891/787

1.5(+0.2/-0.1)

839/785

Spectral analysis: Cooling Flow

indication for a CF

tcool kT / ne 

+

Surface Brightness

Temperature

cooling radius:rcool ~ 80 kpc

  • in the CF model: existence of a minimum T
  • the extra emission comp. can be well modelled either as a CF or a second T comp.
cavity analysis
Cavity analysis

Parameter

1 comp. (MEKAL)

2 comp.

(MEKAL+MEKAL)

kT (keV)

5.2(+0.4/-0.3)

3.5(+1.0/-1.0)

-

cavity N

-

13 (+25/-5)

0.85 Norm

2/ dof

394/313

385/311

Spectral analysis: Cavities

What fills the cavities?

relativistic electrons 

 also hot, dilute thermal plasma?

Chandra + VLA (McNamara et al. 2005)

kThigh(keV)

Normhigh

Indication on the existence of a hot thermal component, but no strong constraints

nfw fit
NFW fit

NFW fit

scaled temperature
Scaled temperature

MS0735

Scaled temperature profile (deprojected)

r t m t
r-T & M-T

Simulations/observations:

<TX>

T

1.51

1/2

 r2500 = 0.79 (1+z )-3/2 h70-1Mpc

1 keV

10 keV

(Navarro et al. 1996)

mean (CF corrected) emission-weighted temperature

[ 470 ]

 M2500 = 1.52  1013 h70-1M

(Ettori et al. 2002)

[ 1.77 ]

Scaling relations: r-T and M-T

Theoretical predictions on cluster formation and evolution:

r  <TX>1/2

<TX> = 5.4 keV  r2500  435 kpc

M  T3/2

T2500= 5.2 keV  M2500  1.851014M

Results in agreement with relations predicted from scaling laws

f gas
f_gas

Gas mass fraction

scaled f gas
Scaled f_gas

Scaled gas mass fraction

comparison chandra
Comparison Chandra

Comparison with Chandra

Projected Temperature

Deprojected Temperature

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