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 = -0.040.03, 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 0.570.21, in reasonable agreement with SP synthesis models
(≈ 1)
c-M relation for groups
We obtain a slope α=-0.2260.076, 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
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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
LT2 slope expected for
self-similar systems.
In practice, LT3 for clusters
(Edge & Stewart 1991),
with possible further
steepening to LT4 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 KT2/3,
rather than the selfsimilar scaling of KT.
KT
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