Collaborators: - Brian McNamara (Waterloo University & Ohio

University) - Paul Nulsen (Harvard-Smithsonian Center for Astrophysics)

Myriam Gitti Myriam Gitti (UniBO,INAF-OABo)(UniBO,INAF-OABo)

X-ray cavities in galaxy clusters

Arcetri, 7 Maggio 2009

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?

Introduction

Galaxy clusters

X-ray visual

100 kpc

• 100-1000 galaxies + intracluster medium (ICM) + dark matter (DM)

• total mass ~ 1014 - 1015 M • size ~ some Mpc

Galaxy clusters are key objects for cosmological studies

Why do we study galaxy clusters?

Millennium Run

(Springel et al. 2005)

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

Radio emission

X-ray emissio

n

Optical emissi

on

magnetic fields

galaxies ICMdark

matter

~2% ~13%

~85%

relativisticparticles

thermal

plasma

Galaxy Clusters (total mass)

AGN radio loud

Radio emissi

on

galaxies ICM

~2% ~13%

thermal

plasma

Galaxy Clusters (total mass)

AGN radio loud

Radio emissi

on

X-ray emissio

n

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

elements

It emits in X-rays by thermal bemsstrahlung + lines

Jbr Z2 neni T-1/2 e–h/kT

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)

ICM temperature ~ 0.5–15 keV

ICM density ~ 10-4 -10-2 cm-3

ICM metallicity ~ 0.3 solar

Luminosity ~ 1043-1046 ergs/s

• Chandra extremely good spatial resolution (~0.5’’)

• XMM-Newton exceptional collecting area and thus sensitivity,

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

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.

Modern X-ray Observatories

Cooling Flow (CF) – standard modelcooling time tcool : characteristic time of energy radiated in X-rays cooling radius rcool: radius at which tcool= age of the cluster

H0-1

Within rcool, tcool < H0

-1 the cooling gas flows inward - with a mass inflow rate M - and is compressed

hydrostatic eq.

CF cluster

non-CF cluster

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

S(r) = S0 [ 1+ (r/rcore)2 ]1/2-3

ICM density distribution:

Surface brightness profile:

ratio of energy per unit mass in

galaxies to that in gas

2/3=2

mH

kT

-model

(Cavaliere & Fusco Femiano 1976)

Compression density increases X-ray emissivity increases

CF cluster

non-CF cluster

CF – observations• low temperature

evidence of cooling

• short cooling time • high density

• H filaments • molecular gas • OVI

CF – observations

Lack of very cold gas

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

Gas drops to Tmin~ 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?

XM~M••

- absorption

- mixing

- inhomogeneous metallicity

• Signature of cooling below 2 keV suppressed

missing soft LX ~

LUV

CF problem - possible solutions

M ~ 0.1 MX

- central AGN - thermal conduction- subcluster merging- combinations/other...

• Heating to balance cooling

X-ray cavities and radio bubbles

• most CF clusters contain powerful radio sources associated with cD

• central ICM shows “holes” often coincident with radio lobes (Chandra)

AGN / ICM interaction

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

3C317 – A2052

Perseus

A2052

RBS797

Fabian et al. 2000

Fabian et al. 2000

Blanton et al. 2001

Blanton et al. 2001

Gitti et al. 2006

Gitti et al. 2006

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

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

rises

Cavity energy

r t = r/v

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

total AGN power

(Birzan et al. 2004)

Cavity properties

• diameter 20-200 kpc

• pV = 1055-1061 erg

• ages = 107-108 yr

• P = 1041-1046 erg/s(Birzan et al. 2004)

(Rafferty et al. 2006)quenching of CFs

trend: feedback

Self-regulated feedback loop

Cooling Flow

AGN outburst

system settles down

cooling and accretion onto a

central BH

cooling is reestablishe

d

cooling is arrested

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

The most powerful AGN outburst Supercavities (~100s kpc) found in MS0735+7421, Hercules A, and

Hydra A

McNamara & Nulsen

ARA&A 2007

substantial contribution to the pre-heating problem ?

Problems addressed

common solution to CF problem and galaxy formation ?

what gives support to the cavities ?

do cavities affect the general cluster properties ?

L T2 gravity

(Markevitch 1998)

L T2.6

L-T relation

(Benson et al. 2003)

Luminosity function of Galaxies

the most powerful AGN outburst as seen by XMM

MS0735

MS0735+7421:

Cavities

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

erg/s

1‘ = 210 kpcH0 = 70 km/s/Mpc

M = 1- = 0.3

Surface brightness profile

undisturbed cluster

60-180 kpc

deficit of emission in the N sector

N sectorN sector

Undisturbed

Undisturbed

Fit with a -model

Undisturbed

Undisturbed

Single -model not a good description of entire profile

fit

strong excess in the centre when

compared to the model

Fit to outer region:

rcore = 195 kpc = 0.77

Temperature profile

Obs. spectrum (r) = spectra in shells

deprojection analysis

line of sight

r

Density profile

Obs. spectrum (r) = spectra in shells

deprojection analysis

line of sight

r

Mass profile

assumption of spherical symmetry

-kTrGmp

d lnne

d lnr

d lnT

d lnrMtot(<r) = +

Eq. hydrostatic equilibrium: P = - ....

ne (r)

from -model or

deprojection

Total gravitational mass Mtot(<r) :

d P

d r

G M(<r)

r 2= -

Mass profile: from -model

From T(r) & ne(r)

Total gravitational mass M(r)

assumption of

hydrostatic eq.

assumption of spherical symmetry

if density follows -model:

ne(r) = ne,0 [ 1+ (r/rc)2 ]-3/2

kr2

Gmp

3rT

r2+rc2

dT

dr

Mtot(<r) =

Mass from beta

Mass profile: from deprojectionFrom T(r) & ne(r)

Total gravitational mass M(r)

assumption of

hydrostatic eq.

assumption of spherical symmetry

if density and pressure are measured from

deprojection analysis

1G

r2

nem

p

dPdr

Mtot(<r) =

What fills the cavities?Radio lobes relativistic electrons

Pext 10 Pradio,eq

Chandra + VLA (McNamara et al.

2005)

Chandra + VLA (McNamara et al.

2005) cavity N

also hot, dilute thermal plasma?

indication of13 KeV component

BUT

poor photon statistics does not allow us to claim a

detection

shock front

post-shocked gas

pre-shocked gas

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

shock front

~ 10% temperature rise

expected by shock model

Mach number M 1.4

Shock front

do (super-)cavities affect the average properties

of galaxy clusters?

Discussion

MS0735+7421:

Overdensity =

3 Mtot(<r)

4 c,z r3

where c,z =

3 Hz2

8 G

Determination of r200 and r2500

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

0.16 0.08

1.77 0.82

465 160

2500

0.11 0.06

15.6 8.78

2230 650

200

fgas,

(Mgas/Mtot)

Mtot,

(1014 M)

r

(kpc)

virial radius rvirr200

Scaled temperature profile (=2500)

(Allen et al. 2001)

6 relaxed clusters observed with Chandra

T2500 = 5.5 - 16 keV

MS0735

r2500 = 465 kpc

T2500 = 5.2 keV

(Vikhlinin et al. 2004)

Scaled temperature profile (=2500)

MS0735 r2500 = 465 kpc

<TX> = 4.7 keV

12 relaxed clusters observed with Chandra

<TX> = 1.6 – 8.9 keV

• 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

Scaled metallicity profile (=180)

MS0735

9 CF clusters observed with BeppoSAX

H0 = 50 km/s/Mpc

=1, =0

(De Grandi & Molendi 2001)

Luminosity vs. Temperature

LT2 gravity

(Markevitch 1998)

LT2.6

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

1. early star formation ?

2. AGN (early / late) ?

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

Luminosity vs. Temperature

CF and cavities:

1. cool gas lifted by outburst

2. compression in the shells

* WARNING! *

Bias for flux-limited surveys

Anomalous L-T effect:

MS0735 factor ~2 more luminous than expected from its temperature

MS0735

(Markevitch 1998)

Rin

in

LL L’Cavity expansion

ICM compression in shells

depends on cavity radius & shell thickness

25 % for MS0735

LX boost by cavities

Luminosity vs. Temperature

“cavity effect” 25

%

* WARNING! * Overestimate fgas

(Voigt & Fabian 2006)

r/r2500

MS0735

Vikhlinin et al. 2005 :

CMB :

MS0735: fgas,2500=0.1650.0

40

fgas,2500=0.1170.002

fgas,2500=0.0910.002

b/

m=0.1750.023

Allen et al. 2004 :

Gas mass fraction

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

Conclusions

Gitti et al. 2007, ApJ, 660, 1118

Gitti et al. 2007, ApJ, 660, 1118

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

…in the future…

Further explanations

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

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)

data

Metallicity profile

Projected DeprojectedMetallicity

cooling radius: rcool ~ 80 kpc

891/787 2 / dof

-kTlow (keV)

- M (M/yr)

3.9 (+0.1/-0.1)

kT (keV)

1 isoth comp. (MEKAL)

Parameter

•

+indication for a CF

tcool kT / ne

Surface Brightness Temperatur

e

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.

Spectral analysis: Cooling Flow

7.6 (+0.5/-1.3)

260 (+30/-20)

1.5 (+0.2/-0.1)

839/785

CF (MEKAL+MKCFLOW

)

6.1 (+1.3/-0.6)

0.73 Norm

2.3 (+0.4/-0.4)

839/785

2 isot comp.

(MEKAL+MEKAL)

Normlow

CF analysis

Spectral analysis: Cavities

385/311 394/313 2 / dof

--

3.5 (+1.0/-1.0) 5.2 (+0.4/-0.3)

kT (keV)

2 comp. (MEKAL+MEKAL)

1 comp. (MEKAL)

Parameter

kThigh (keV)

Normhigh

What fills the cavities?

relativistic electrons

Chandra + VLA (McNamara et al.

2005)

Chandra + VLA (McNamara et al.

2005)

also hot, dilute thermal plasma?

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

cavity N

13 (+25/-5)

0.85 Norm

Cavity analysis

NFW fit NFW fit

MS0735

Scaled temperatureScaled temperature profile

(deprojected)

Scaling relations: r-T and M-T

r <TX>1/2

mean (CF corrected)

emission-weighted temperature

M T3/2

<TX> = 5.4 keV r2500 435 kpc

T2500= 5.2 keV M2500 1.851014 M

[ 470 ]

[ 1.77 ]

Results in agreement with relations predicted from scaling laws

Theoretical predictions on cluster formation and evolution:

r2500 = 0.79 (1+z )-3/2 h70-1

Mpc (Navarro et al. 1996)

<TX>

10 keV

1/2

M2500 = 1.52 1013 h70-1

M (Ettori et al. 2002)

T

1 keV

1.51

Simulations/observations:

r-T & M-T

Gas mass fractionf_gas

Scaled gas mass fractionScaled f_gas

Comparison with Chandra

Projected Temperature Deprojected Temperature

Comparison Chandra

XMM image large

Chandra image