Transcript Slide 1
MASS AND ENTROPY PROFILES OF X-RAY BRIGHT RELAXED GROUPS FABIO GASTALDELLO UC IRVINE & BOLOGNA D. BUOTE P. HUMPHREY L. ZAPPACOSTA J. BULLOCK W. MATHEWS UCSC F. BRIGHENTI BOLOGNA OUTLINE 1. MASS RESULTS AND c-M PLOT FOR X-RAY GROUPS 2. ENTROPY PROFILES 3. AGN FEEDBACK: THE CASE OF AWM4 DM DENSITY PROFILE 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). Navarro et al. 2004 c-M RELATION •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). Bullock et al. 2001 Selection Effects Wechsler et al. 2002 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) A SPECIAL ERA IN X-RAY ASTRONOMY Chandra •1 arcsec resolution XMM-Newton •High sensitivity due to high effective area, i.e. more photons Clusters X-ray results Pointecouteau et al. 2005 Vikhlinin et al. 2006 • 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). THE 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. SELECTION OF THE SAMPLE 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. RESULTS •After accounting for the mass of the hot gas, NFW + stars is the best fit model MKW 4 NGC 533 RESULTS •No detection of stellar mass due to poor sampling in the inner 20 kpc or localized AGN disturbance Buote et al. 2002 NGC 5044 RESULTS •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) c-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 • Buote et al. 2007 c-M relation for 39 systems ranging in mass from ellipticals to the most massive galaxy clusters (0.0620) 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 WMAP 1 yr Spergel et al. 2003 THE X-RAY c-M RELATION WMAP 3yr Spergel et al. 2006 CAVEATS/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 Extend the profiles at large radii (r500 is possible to reach for groups) MASS 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 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 relation 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) Mulchaey 2000 X-ray surface brightness 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. Ponman, Cannon & Navarro 1999 Entropy 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 selfsimilar scaling of KT. KT PROPOSED EXPLANATIONS 1. 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 PROFILE FROM GRAVITATIONAL STRUCTURE FORMATION VOIT ET AL. 2005 COMPARISON WITH MASSIVE CLUSTERS AND GRAVITATIONAL SIMULATIONS PRATT ET AL. 2006 ENTROPY PROFILES ENTROPY PROFILES GASTALDELLO ET AL. 2008, IN PREP. ENTROPY PROFILES GASTALDELLO ET AL. 2008, IN PREP. COMPARISON WITH MASSIVE CLUSTERS AND GRAVITATIONAL SIMULATIONS GASTALDELLO ET AL. 2008, IN PREP. COMPARISON WITH MASSIVE CLUSTERS AND GRAVITATIONAL SIMULATIONS GASTALDELLO ET AL. 2008, IN PREP. GAS FRACTIONS ENTROPY 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 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 AGN FEEDBACK “I’VE BEEN ESPECIALLY IMPRESSED BY THE CHANDA X-RAY IMAGES OF GALAXY CLUSTERS. WE SEE HOW GAS IS COOLING DOWN AND HOW THE COOLING IS BEING BALANCED BY TREMENDOUS OUTBURSTS OF JETS AND BUBBLES. THIS IS SOMETHING THAT MOST PEOPLE DIDN’T SUSPECT WAS HAPPENING UNTL THESE IMAGES REEALED IT ” Martin Rees AGN 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) AWM4 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 Gas cools AGN stops being fed AGN feedback Gas heated AWM4 AND AGN FEEDBACK GASTALDELLO ET AL. 2007 AWM4 AND AGN FEEDBACK AWM4 AND AGN FEEDBACK CONCLUSIONS ON AGN FEEDBACK 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