Transcript ppt

APEX S-Z observations
of the XMM-LSS field
Marguerite PIERRE (CEA Saclay)
Rüdiger KNEISSL (Berkeley)
Clusters of galaxies
Center of Abell 2218 viewed by HST
z = 0.176
Dark matter: Zwicky 1933
X-ray emission from clusters
• MASS fractions:
• Dark matter : 80%
• Hot gas : 15%
• Galaxies : 5%
• Theory’s pov
A cluster of galaxies =
an object with a MASS
of ~1014-16 Mo
Cosmology with clusters
0<z<2
Clusters are the most massive
entities of the universe
Trace the node of the cosmic
structure = potential wells
(much better than galaxies!)
Constraints on cosmology from clusters are complementary
to those provided from the CMB and the SN :
they do not rely on the same physical phenomena
An example
Priors:
Wbh2 = 0.0214 +/- 0.002
h = 0.72 +/- 0.08
Rappeti et al 2005
Plan of the talk: close to
the first joint X-ray/S-Z survey
on large scales
1.
Reminder on the S-Z effect and its
cosmological applications
2.
The Apex S-Z instrument
3.
Observations of the XMM-LSS field
What will we get?
What will we be able to say about cosmology?
The S-Z thermal effect
APEX frequencies
(from Carlstrom + Bertoldi)
S-Z versus X-ray

SZ : DTCMB ≈ ∫ neTe dl
(independent of z – integrated pressure)
Integrated SZ (over solid angle)
≈ N<T> /DA2 ≈ M<T> /DA2

X-ray emissivity : e ≈ n2T1/2 dV
Flux (over cluster volume)
≈ ∫edV /DL2 ≈ L/DL2
Cosmological applications
of the S-Z effect

Evolution of the number density of clusters +
space distribution
• Underlying cosmology
• Equation of state of the dark energy

S-Z + X-ray
• Hubble constant
• Angular diameter distance relation out to z~2
• Cluster gas mass fraction => Wm, distance indicator
Caveat !

In order to constrain cosmology, we must
understand how clusters evolve
• The detected N(M,z) is not only a result of
gravitational physics.
• M->T-> Lx (z) ,
ngaz(z)
The evolution of the physics of the ICM is a key
issue: accretion, shocks, feedback, cooling...
 for the S-Z and X-ray domains, we must have – or
determine – mass-observable relations at any z
The S-Z reciever (Berkeley)
330 elements (TES Bolometers)
Commissioning of the full array in spring 2006
Operating l : 2mm (150 GHz), 90 and 220 planned
A few numbers (1)

Apex +tertiary optics built in Berkeley:
• FWHM = 1arcmin

XMM
• FWHM = 6” (on-axis)

Cluster core radius of 250 kpc
•
•
•
•
2.3’ at z =0.1
41” at z = 0.5
31” at z= 1
28” at z= 2
A few numbers (2)

Apex S-Z sensitivity :
• 10 mk

XMM point source sensitivity in 10 ks
exposure :
• 5E-15 erg/s/cm2 in [0.5-2] keV
The XMM-LSS field
Current multi-l coverage
XMDS & VVDS deep
VVDS wide
XMM Subaru Deep Survey
SPITZER Legacy :
SWIRE
NOAO Deep Survey
X-ray data status:
Galex
- Received - received - received
- Planned
and covered by W1 CFHTLS, VLA and Integral
The XMM-LSS/CFHTLS/SWIRE field :
an XMM Large Programme
XMM pointings :
. Done
. To be redone
. Subaru DS (done)
. To be done in
2006-2007
Square =
SWIRE 10deg2 field
Scuba 2 Legacy
A piece of the XMM-LSS mosaic
~ 1x2 deg2
RASS sources
Image by A. Read
10 ks exp.
red [0.3-1] keV
green [1-2.5] keV blue [2.5-10]keV
Constructing a COMPLETE
cluster sample with XMM
 Suitable for cosmological studies
 Selection effects controlled
 a priori : NOT flux limited sample
• Clusters span a range of sizes and profiles
• Measured flux  Emitted flux
• groups at 0.3< z < 1
Detection rates
Core radius (arsec)
Pacaud et al 2006
Countrate
The cluster selection function


Is monitored via extensive
simulations
In the following, we a assume a
simple flux limit.
CFHTLS Images of D1 clusters
C1 z=0.05
CFHTLS Images of D1 clusters
C1
z=0.31
CFHTLS Images of D1 clusters
C1 z =1.05
Physics of the XMM

For the first time,
• the XMM-LSS detects the group (T<2
keV) population out to z=0.5
• We measure the L-T relations of these
objects
•  light on the ICM physics!
The L-T relation
1
4 keV
T
______ L-T at z=0
-------- L-T at z=0.5 (self-similar evolution)
A few numbers (3)

Coverage of the 10 deg2
• XMM : ~ 1Ms ~ 12 days
• Apex : ~ 2 weeks

Cluster number density
• XMM: ~ 15 clusters/deg2
• Apex: 4 clusters/deg2 (> 2-3 E14 Mo)
 How do the n(z) compare ?
10 mk  y=0.5 E-4 arcmin2
Influence of the low-end of the
mass function (X-ray clusters)
Pacaud et al, in prep
Influence of the X-ray flux limit
Pacaud et al, in prep
Influence of the cosmological
parameters on n(z)

Example for X-ray clusters

Similar behaviour for S-Z clusters
Influence of the cluster evolution
Pacaud et al, in prep
Influence of the equation of state
of the Dark Energy
Pacaud et al, in prep
Combining XMM and Apex


Ho / Da comparison vs cosmology
Use the joint data sets to get insights into the
evolution of the ICM physics
• S-Z  integrated pressure along the line of sight
• X  L-T (z) relation

Add mass information from the weak lensing
survey on the CFHTLS data (Refregier et al, in prep)

Calibrate mass-observables relations

Hints on the cosmology
Apex S-Z survey to start by
Spring 2006