X-ray cavities in galaxy clusters
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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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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

    • 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?



  • Galaxy clusters

    X-ray

    visual

    100 kpc

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

    • total mass ~ 1014 - 1015 M

    • size ~ some Mpc


    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


    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


    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


    • 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)


    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’)


    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


    CF– observations

    • short cooling time

    • high density

    • low temperature

    • H filaments

    • OVI

    • molecular gas

     evidence of cooling


    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?


    - 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



    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”


    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


    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


    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)


    cooling and accretion onto a central BH

    Cooling Flow

    AGN outburst

    cooling is reestablished

    cooling is arrested

    system settles down

    Self-regulated feedback loop


    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


    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


    1‘ = 210 kpc

    H0 = 70 km/s/Mpc

    M = 1- = 0.3

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

    Cavities


    deficit of emission in the Nsector

    Surface brightness profile

    N sector

    undisturbed cluster

    60-180 kpc

    Undisturbed


    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


    r

    line of sight

    Obs. spectrum (r) = spectra in shells

     deprojection analysis

    Temperature profile


    r

    line of sight

    Obs. spectrum (r) = spectra in shells

     deprojection analysis

    Density profile


    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


    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


    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


    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?


    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?


    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)


    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)


    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)


    MS0735

    Scaled metallicity profile (=180)

    9 CF clusters observed with BeppoSAX

    H0 = 50 km/s/Mpc

    =1, =0

    (De Grandi & Molendi 2001)


    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


    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)


    Rin

    in

    depends on cavity radius & shell thickness

     25 % for MS0735

    Cavity expansion

    ICM compression in shells

    L L’

    L

    LX boost by cavities


    “cavity effect”  25 %

    * WARNING! * Overestimate fgas

    Luminosity vs. Temperature


    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


    …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


    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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