Transcript Cosmology with Future Galaxy Cluster Surveys

A Primer on SZ Surveys
Gil Holder
Institute for Advanced Study
Outline
• Sunyaev-Zel’dovich effect
• Upcoming surveys
• What’s next?
Optical Image of Cl 0016+16
(Clowe et al. 2000)
~ 7’
~ 2 h-1 Mpc
Hot Gas in Cl 0016+16
(Reese)
kT ~ 7.5 keV
Sunyaev-Zel’dovich Effect
I
CMB
Hot
electrons
CMB+
Optical depth: τ ~ 0.01
Fractional energy gain per scatter:
kT
~ 0.01
2
me c

SZ Observables I
Along a line of sight:
T
 g ( )  dl
T
 kT 
n (l ) T

2  e
 mec 
DEPENDS ONLY ON CLUSTER PROPERTIES !!!!
Independent of redshift
Temperature weighted electron
column density
Unique spectral signature
Non-Thermal Spectrum
Abell 2163
Data from 3
experiments
SZ Observables II
Integrated effect from cluster:
1
S   T d 
n kT dV
2  e
d A ( z)
 proportional to total thermal energy of electrons
 Temperature weighted electron inventory
 angular diameter distance, not luminosity
distance
SZ Observables III
In reasonable units ( i.e., 1/h):
S
fgh
d A ( z)
2
M T 
Assume a virial relation: T   M
S
fgh
d A ( z)
2
M
2/ 3
5/3
uncertainties come in mass limit as ^(0.6)
SZE Regularity
Metzler ; astro-ph/9812295
dTo
Central decrement vs
Mass – 40% scatter
<dT>
Average SZ flux vs
Mass – 10% scatter
Searching for Galaxy Clusters
Small area; very deep
- AMI, AMIBA, BOLOCAM, SZA
Large area; relatively shallow
- ACBAR, PLANCK
Large area; very deep
- ACT, SPT
Mass Limits
Fluxes at 30
GHz
PLANCK
SZA
Foregrounds
• CMB – need good angular resolution and/or good
spectral resolution; problem at all SZ frequencies
• Radio point sources – need good angular
resolution for frequencies <90 GHz
• Dusty point sources – need good angular
resolution and/or spectral resolution at frequencies
>200 GHz
• Radio halos and ghosts – could be a problem at
frequencies < 15 GHz
SZA
• Survey 10 square degrees to a few uK at
resolution of 2-3 arcminutes at 30 GHz
• Expected mass limit ~ 1014 h 1M 
• Follow up catalog at 90 GHz for high
resolution (<20”)
• 100 – 500 clusters expected
Example: RXJ1347-1145
Reese
X-ray (colours)
SZ (contours)
SZ only
CMB contamination??
• clusters are clearly
at a different spatial
scale
• close amplitudes
means beam dilution
catches up fast !!!
Roughly 1 deg x 1deg – labels are uK
Cosmology With the SZA
Holder, Haiman &
Mohr 2001
Dark Energy With the SZA
• 12 square degrees
• assume NO
systematic errors
• assume redshifts
measured to z=2
PLANCK
• Survey the full sky to a few uK at resolution
of 5-10 arcminutes at many frequencies
• Expected mass limit ~8 1014 h1M 
• Cluster detections will be unresolved –
point sources with SZE-like spectra
• 1000 – 50000 clusters expected
Cosmology With Planck
Black: all z
Red: z<0.5 only
Holder, Haiman &
Mohr 2001
SPT/ACT/???
• Survey ~1000 square degrees to a few uK at
resolution of 1-2 arcminutes at several
frequencies
14 1
• Expected mass limit ~2.5 10 h M 
• Most powerful for cosmology
• 5000 – 200000 clusters expected
Cosmology with the SPT
Holder, Haiman &
Mohr 2001
dN/dz for SPT
Dark Energy With the SPT
Also sensitive to
time dependent
equation of state
(Weller, Battye &
Kneissl 2001)
Possible Plan of Action
1) Use AMI/AMIBA/BOLOCAM/SZA to
define a significant SZE-selected sample
2) Follow up at many wavelengths: optical,
X-ray, radio, cm, mm (including SZA!)
3) Do a very large, deep survey for precise
measurements of cosmological parameters
On the Horizon
uK imaging between 30-400 GHz with arcminute resolution
-- SPT, ACT, dedicated interferometers, ALMA, etc.
New science opportunities & challenges
-- peculiar velocities,
-- spectral SZ
-- CMB lensing
Peculiar Velocities (Kinetic SZ)
• Pure redshift, blueshift => thermal spectrum
T
v
  
T
c
Arcminutes scales => CMB ~ 1 uK
-- CMB noise contribution = 10 km/s (0.01/τ)
Other contamination: 50 km/s ?
(Fischer & Lange 1993)
Relativistic Corrections
Lensing of the CMB
Typical CMB gradient
-- 15 uK/arcmin
Typical deflection angle
-- ~ 0.1-1 arcmin
(Seljak and Zaldarriaga )
Summary
• New cluster surveys coming soon
• Detailed follow-up will be required of some
sample of SZE-selected clusters
• Ambitious survey machines in proposal
stages could be extremely powerful
Z=0.83
Gallery of SZ Images
Z=0.14
M lim  5x1014 h1M sun
Green: shift
in matter
density by
10%
Holder &
Carlstrom 2001
Counting Galaxy Clusters

dN
dn
dV
 
dM
dzd  M lim dM
dzd 
Mass limit
Mass
function
(Jenkins, Press-Schechter)
Volume
element
Self-Similar Evolution
Holder &
Carlstrom 2001
Effects of Gas Evolution
Holder &
Carlstrom 2001
Angular Power Spectrum of SZ
Sources
Holder &
Carlstrom 2001