Transcript Slide 1
TWO SAMPLES OF X-RAY
GROUPS
FABIO GASTALDELLO
UC IRVINE & BOLOGNA
D. BUOTE
P. HUMPHREY
L. ZAPPACOSTA
J. BULLOCK
W. MATHEWS UCSC
F. BRIGHENTI BOLOGNA
OUTLINE / MOTIVATION
1. MASS PROFILES AND c-M PLOT FOR A SAMPLE OF
X-RAY BRIGHT AND RELAXED GROUPS
2. ENTROPY PROFILES FOR THE SAME SAMPLE.
RELEVANT SCALE FOR BREAKDOWN OF SELFSIMILARITY
3. PRELIMINARY RESULTS ON A FLUX-LIMITED SAMPLE
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).
rvir calculated using Bryan &
Norman 98 for concordance
model
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
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
ENTROPY PROFILES
ENTROPY PROFILES
ENTROPY PROFILES
THE BASELINE INTRACLUSTER ENTROPY
PROFILE FROM GRAVITATIONAL
STRUCTURE FORMATION
VOIT ET AL. 2005
COMPARISON WITH MASSIVE CLUSTERS
AND GRAVITATIONAL SIMULATIONS
PRATT ET AL. 2006
COMPARISON WITH MASSIVE CLUSTERS
AND GRAVITATIONAL SIMULATIONS
COMPARISON WITH MASSIVE CLUSTERS
AND GRAVITATIONAL SIMULATIONS
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
AWM4 AND AGN FEEDBACK
NOGS (NORAS GROUP SAMPLE)
• Purely X-ray selected flux limited samples have been very effective in
cluster studies
(e.g.,Gioia+90,Edge+90,Rosati+95,Scharf+97,Vikhlinin+98,Romer+00,Bo
hringer+00) and they have follow-up studies with XMM or Chandra
(REXCESS,400d2)
• Groups have been historically selected in the optical band, only one
pioneering study of 8 groups from the ROSAT NEP survey (Henry+95)
• We used the NORAS catalogue:
1. 10h20m-14h region due to superior re-analysis
2. fx > 3x10-12 erg cm-2 s-1, completeness to better than 82%
3. Lx < 5x1043 erg s-1
• 15 objects, 5 in the archive, 10 observed with a Chandra LP (400ks, PI
Buote)
NOGS (NORAS GROUP SAMPLE)
NOGS (NORAS GROUP SAMPLE)
A 1142
A 1275
A 1185
A 1377
NOGS (NORAS GROUP SAMPLE)
NGC 4104
A 1314
NGC 5129
RXJ 022
NOGS (NORAS GROUP SAMPLE)
A 1177
RGH 80
SUMMARY
• DETAILED MASS PROFILES FOR A SAMPLE OF X-RAY
BRIGHT GROUPS ARE WELL FITTED BY NFW+STARS. THE XRAY c-M RELATION POINTS TO A COMPROMISE WMAP
COSMOLOGY (EVRARD ET AL. 07, YEPES TALK)
•BROKEN POWER LAW BEHAVIOR OF ENTROPY PROFILES
POINTS TO MORE IMPORTANT LOCAL MODIFICATIONS
(AGN)
•STAY TUNED FOR RESULTS FOR A COMPLETE X-RAY
SELECTED, FLUX LIMITED SAMPLE (AND MORE FUN TO
COME WITH XMM-LSS AND COSMOS)