Transcript Slide 1

THE X-RAY C-M RELATION
FABIO GASTALDELLO
INAF-IASF MILANO, UCI
D. BUOTE, S. ETTORI, P. HUMPHREY, L. ZAPPACOSTA, A.
LECCARDI, S. MOLENDI, M. ROSSETTI, J. BULLOCK, M.
MENEGHETTI, W. MATHEWS, F. BRIGHENTI
OUTLINE
1. INTRODUCTION: c-M AS COSMOLOGICAL TOOL
2. c-M RELATION FOR THE LOCAL SAMPLE
3. c-M FOR THE SAMPLE OF 44 CLUSTERS AT z=0.1-0.3
4. CONCLUSIONS
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; Macciò et
al. 2008,M08).
Bullock et al. 2001
c-M RELATION
Macciò et al. 2008
X-RAY MASS DETERMINATION
• Spectra averaged within circular annuli
• Normalization / shape of spectrum gives gas density /
temperature
X-RAY MASS DETERMINATION
A) Deproject with no need to assume parametrized
quantities for gas quantities but smoothing required
to obtain a physical mass profile (smoothed inversion)
B) Forward-fitting: fit gas density and temperature
simultaneously assuming only parameterizations for
density (or T or entropy) and mass
Buote & Humphrey 11
RESULTS
•After accounting for the mass of the hot gas, NFW (+ stars) is
the best fit model
STARS
GAS
MKW 4
DM
NGC 533
THE LOCAL X-RAY c-M RELATION
• Buote, Gastaldello 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 (slope
-0.172 ± 0.026)
• Normalization and
scatter consistent
with relaxed objects
THE LOCAL X-RAY c-M RELATION
WMAP 1 yr
Spergel et
al. 2003
THE LOCAL X-RAY c-M RELATION
WMAP 3yr
Spergel et
al. 2006
c-M relation for groups
We obtain a slope α=-0.2260.076, c decreases with M at the 3σ level
THE SAMPLE @ z = 0.1 – 0.3
• In Ettori, Gastaldello et al. (2010) we used the sample from Leccardi &
Molendi (2008), all hot clusters (kT > 3.3 keV) in the range 0.1 < z < 0.3,
with detailed temperature profiles secured by performing accurate
background modelling
•Even though clusters showing evidence of recent and strong interactions
were excluded, we have not only regular and relaxed clusters in the
sample. They are characterized by the entropy ratios, following Leccardi
et al. (2010), which are closely related to the dynamical disturbance
A 2204 LEC
A 1763 HEC
c-M @ z = 0.1 – 0.3
c-M @ z = 0.1 – 0.3
Slope steeper than
predicted by simulations, it
can not be constrained in
the narrow mass range (all 0.50 ± 0.07, LEC -0.28 ±
0.15).
Normalization in
agreement.
Constraints improve when
considering only clusters
with rs within the data and
only LEC clusters.
Concentration biased high
in disturbed systems (e.g.,
Lau et al. 2009).
COSMOLOGICAL CONSTRAINTS
OPEN ISSUES
• HYDROSTATIC EQUILIBRIUM
• SELECTION EFFECTS
• RADIAL RANGE OF DATA TO OBTAIN MASS PROFILE
• THEORETICAL/SIMULATION PREDICTION
• ADIABATIC CONTRACTION
BIAS IN HE DERIVED c
Lau et al. (2009)
TURBULENT PRESSURE RISING W/ RADIUS AND MORE
IMPORTANT IN DISTURBED OBJECTS. SEE RASIA ET AL.,
MENEGHETTI ET AL.
SELECTION EFFECTS
Wechsler et al. 2002
De Boni et al. 2013
WHAT ARE WE REALLY SELECTING WHEN WE SELECT
“RELAXED” OBJECTS ?
RADIAL RANGE OF DATA
RXJ 1159
Humphrey et al. (2012)
SUMMARY & CONCLUSIONS
•c-M relation as determined from X-rays has provided independent
evidence of hierarchical structure formation, in particular when fitted
over a wide range of masses
•c-M relation offers interesting and novel approach to potentially
constrain cosmological parameters. Selection effects, HE, radial range of
the data, response of DM to baryons (adiabatic contraction) and semianalytic/ N-body simulations are open issues which have to be better
characterized and improved.