MASS AND ENTROPY PROFILES OF X-RAY BRIGHT RELAXED GROUPS

MASS AND ENTROPY PROFILES MASS AND ENTROPY PROFILES OF X-RAY BRIGHT RELAXED OF X-RAY BRIGHT RELAXED

GROUPS GROUPS

FABIO GASTALDELLO

UC IRVINE & BOLOGNAD. BUOTE

P. HUMPHREY

L. ZAPPACOSTA

J. BULLOCK

W. MATHEWS UCSC

F. BRIGHENTI BOLOGNA

OUTLINEOUTLINE

1. MASS RESULTS AND c-M PLOT FOR X-RAY GROUPS

2. ENTROPY PROFILES

3. AGN FEEDBACK: FOCUS ON SOME PARTICULAR OBJECTS

DM DENSITY PROFILEDM DENSITY PROFILE

Navarro et al. 2004

The concentration parameter c do not depend strongly on the innermost data points, r < 0.05 rvir (Bullock et al. 2001, B01; Dolag et al. 2004, D04).

c-M RELATIONc-M RELATION

Bullock et al. 2001

•c slowly declines as M increases (slope of -0.1)

•Constant scatter (σlogc ≈ 0.14)

•the normalization depends sensitively on the cosmological parameters, in particular σ8 and w (D04,Kuhlen et al. 2005).

Concentrations for relaxed halos are larger by 10% compared to the whole population (Jing 2000, Wechsler 2002, Maccio’ 2006). They show also smaller scatter (σlogc ≈ 0.10)

Wechsler et al. 2002

Selection EffectsSelection Effects

A SPECIAL ERA IN X-RAY ASTRONOMY

Chandra XMM-Newton

•1 arcsec resolution •High sensitivity due to high effective area, i.e. more photons

• NFW a good fit to the mass profile

•c-M relation is consistent with no variation in c and with the gentle decline with increasing M expected from CDM (α = -0.040.03, P05).

Vikhlinin et al. 2006Pointecouteau et al. 2005

Clusters X-ray resultsClusters X-ray results

THE PROJECTTHE PROJECT

•Improve significantly the constraints on the c-M relation by analyzing a wider mass range with many more systems, in particular obtaining accurate mass constraints on relaxed systems with 1012 ≤ M ≤ 1014 Msun

•There are very few constraints on groups scale (1013 ≤ M ≤ 1014 Msun) , where numerical predictions are more accurate because a large number of halo can be simulated.

In Gastaldello et al. 2007 we selected a sample of 16 objects in the 1-3 keV range from the XMM and Chandra archives with the best available data with

•no obvious disturbance in surface brightness at large scale

•with a dominant elliptical galaxy at the center

•with a cool core

•with a Fe gradient

The best we can do to ensure hydrostatic equilibrium and recover mass from X-rays.

SELECTION OF THE SAMPLESELECTION OF THE SAMPLE

RESULTSRESULTS•After accounting for the mass of the hot gas, NFW + stars is the best fit model

MKW 4

NGC 533

RESULTSRESULTS•No detection of stellar mass due to poor sampling in the inner 20 kpc or localized AGN disturbance

NGC 5044

Buote et al. 2002

RESULTSRESULTS

•NFW + stars best fit model

•We failed to detect stellar mass in all objects, due to poor sampling in the inner 20 kpc or localized AGN disturbance. Stellar M/L in K band for the objects with best available data is 0.570.21, in reasonable agreement with SP synthesis models (≈ 1)

•Adopting more complicated models, like introducing AC or N04 did not improve the fits. AC produces too low stellar mass-to-light ratios

c-M relation for groupsc-M relation for groups

We obtain a slope α=-0.2260.076, c decreases with M at the 3σ level

THE X-RAY c-M RELATION THE X-RAY c-M RELATION • Buote et al. 2007 c-M relation for 39

systems ranging in mass from ellipticals to the most massive galaxy clusters (0.06-20) x 1014 Msun.

• A power law fit requires at high significance (6.6σ) that c decreases with increasing M

• Normalization and scatter consistent with relaxed objects

THE X-RAY c-M RELATION THE X-RAY c-M RELATION

WMAP 1 yr Spergel et al. 2003

THE X-RAY c-M RELATION THE X-RAY c-M RELATION

WMAP 3yr Spergel et al. 2006

CAVEATS/FUTURE WORKCAVEATS/FUTURE WORK HE (10-15% from simulations, e.g. Nagai et al.

2006, Rasia et al. 2006). No results yet on the magnitude for the bias on c (if there is one) due to radial dependence of turbulence

Selection bias Semi-analytic model prediction of c-M Gas physics and AC (problems also with rotation

curves of spirals: Kassim et al. 2006, Gnedin et al. 2006 but also positive claims: M31 mass model of Seigar et al. 2007)

Extend the profiles at large radii (r500 is possible to reach for groups)

MASS CONCLUSIONSMASS CONCLUSIONS

•The crucial mass regime of groups has provided the crucial evidence of the decrease of c with increasing M

•c-M relation offers interesting and novel approach to potentially constrain cosmological parameters

THE RELEVANCE OF ENTROPYTHE RELEVANCE OF ENTROPY

In the widely accepted hierarchical cosmic structure formation predicted by cold dark matter models and in the absence of radiative cooling and supernova/AGN heating, the thermodynamic properties of the hot gas are determined only by gravitational processes, such adiabatic compression during collapse and shock heating by supersonic gas accretion (Kaiser 1986)

clusters and group of galaxies should follow similar scaling relations, for example if emission is bremsstrahlung and gas is in hydrostatic equilibrium L T2 and if we define as “entropy” K = T/n2/3, then K T (so S=k lnK + s0, it’s also called adiabat because P = K ργ).

Entropy reflects more directly the history of heating and cooling of the ICM

The L-T relationThe L-T relation

Mulchaey 2000

It has been clear for many years that the cluster L-T relation does not follow the LT2 slope expected for self-similar systems.

In practice, LT3 for clusters (Edge & Stewart 1991), with possible further steepening to LT4 in group regime (Helsdon & Ponman 2000)

X-ray surface brightnessX-ray surface brightness

Ponman, Cannon & Navarro 1999

Overlay of scaled X-ray surface brightness profiles shows that emissivity (hence gas) is suppressed and flattened in cool (T<4 keV) systems, relative to hot ones.

Entropy in the IGMEntropy in the IGM

Entropy floor

Self-similar scaling

Ponman et al. (1999) & Lloyd-Davies et al (2000) studied ROSAT and ASCA data for a sample of clusters core entropy appeared to show a “floor” at~100-150 keV cm2

at r=0.1 r200 .

Entropy in the IGMEntropy in the IGM

A larger study, of 66 systems by Ponman et al. (2003), now indicates that there is not a “floor” but a “ramp”, with K(0.1r200) scaling as KT2/3, rather than the self-similar scaling of KT.

KT

PROPOSED EXPLANATIONSPROPOSED EXPLANATIONS1. EXTERNAL PREHEATING MODELS: the IGM was heated prior

to the formation of groups and clusters (e.g. Tozzi & Norman 2001) results in isoentropic cores

2. INTERNAL HEATING MODELS: the gas is heated inside the bound system by supernovae or AGN (e.g. Loewenstein 2000)

3. COOLING MODELS: low entropy gas removed from the system, producing an effect similar to heating (e.g. Voit & Bryan 2001)

All three models can reproduce the L-T relation and excess entropy but with some problems:

1 requires too large amount of energy at high redshift

2 requires 100% efficiency from supernovae or fine tuning for AGN

3 overpredicts the amount of stars in groups and clusters

More realistic scenarios with both heating and cooling are required (e.g. Borgani et al. 2002)

External preheating models with different levels of heating. Large isoentropic cores are produced

Internal heating with rising entropy profiles

BRIGHENTI & MATHEWS 2001

THE BASELINE INTRACLUSTER ENTROPY THE BASELINE INTRACLUSTER ENTROPY PROFILE FROM GRAVITATIONAL STRUCTURE PROFILE FROM GRAVITATIONAL STRUCTURE

FORMATIONFORMATION

VOIT ET AL. 2005

COMPARISON WITH MASSIVE CLUSTERS AND COMPARISON WITH MASSIVE CLUSTERS AND GRAVITATIONAL SIMULATIONSGRAVITATIONAL SIMULATIONS

PRATT ET AL. 2006

ENTROPY PROFILESENTROPY PROFILES


GASTALDELLO ET AL. 2008, IN PREP.







GAS FRACTIONSGAS FRACTIONS

ENTROPY CONCLUSIONSENTROPY CONCLUSIONS

BROKEN POWER LAW ENTROPY PROFILES FOR GROUPS WITH STEEPER INNER SLOPES AND FLATTER OUTER SLOPES SEEM TO POINT TO HIGHER IMPORTANCE OF FEEDBACK PROCESSES WITH RESPECT TO MASSIVE CLUSTERS

LOWER GAS FRACTIONS ARE ANOTHER EVIDENCE OF THIS FACT

AGN FEEDBACKAGN FEEDBACK

THE “OLD” MASS SINK PROBLEM IS NOW THE “FEEDBACK PROBLEM”

AGN FEEDBACK, PUT ON A FIRMER GROUND BY THE CHANDRA IMAGES, HAS BROADER ASTROPHYSICAL IMPLICATIONS FOR GALAXY FORMATION AND EVOLUTION

“SOME LOOSE ENDS REMAIN” (J. BINNEY)

NGC 5044 AND NGC 4325NGC 5044 AND NGC 4325

NGC 5044

NGC 4325

ENTROPY PROFILES FOR AGN ENTROPY PROFILES FOR AGN HEATINGHEATING

VOIT ET AL. 2006


NGC 4325 AGN DISTURBANCE: RUSSELL ET AL. 2007

NGC 5044 AND NGC 4325NGC 5044 AND NGC 4325

NGC 5044

NGC 4325

NGC 5044 NGC 5044

NGC 5044 NGC 5044

DUST IN NGC 5044 DUST IN NGC 5044

TEMI, BRIGHENTI & MATHEWS 2007

AWM4 AND AGN FEEDBACKAWM4 AND AGN FEEDBACK

“In this scenario there is a clear dichotomy between active and radio quiet clusters: one would expect the cluster population to bifurcate into systems with strong temperature gradients and feedback and those without either”

Donahue et al. 2005


GASTALDELLO ET AL. 2007, APJ SUBM.



CONCLUSIONS ON AGN CONCLUSIONS ON AGN FEEDBACKFEEDBACK

AGN FEEDBACK HAS ALL THE FEATURES OF THE RIGHT SOLUTION BUT WE ARE NOT CLOSE TO A CLEAR UNDERSTANDING

AGN FEEDBACK IN GROUPS IS STILL POORLY INVESTIGATED AND THERE ARE SOME PUZZLES, LIKE AWM 4

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MASS AND ENTROPY PROFILES OF X-RAY BRIGHT RELAXED GROUPS