Transcript Sunyaev-Zel`dovich Effect (Mark Birkinshaw)

The Sunyaev-Zel’dovich effect
The Sunyaev-Zel’dovich effect
AMI day, 2011 September 30
Mark Birkinshaw
University of Bristol
The Sunyaev-Zel’dovich effect
The thermal SZ effect
The effect comes from the inverse-Compton scattering
of the CMB by the hotter electrons in the ICM.
Thermal SZ effect strength  Comptonization
parameter, ye, the dimensionless electron temperature
weighted by the scattering optical depth.
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The Sunyaev-Zel’dovich effect
The thermal SZ effect
Total SZ flux density
S RJ   d  neTe dz  U thermal
• z-independent measure of ICM thermal energy content
• Virial theorem – measures gravitational potential
energy unless cluster in dynamically-active state
• With X-ray data for electron temperature, get gas mass
and lepton count, hence baryonic mass fraction
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The Sunyaev-Zel’dovich effect
The thermal SZ effect
Now easy to detect for known clusters such
as those from X-ray surveys
e.g., Lancaster et al. (2011) complete
sample of 18 high-LX ROSAT BCS
clusters (Ebeling et al. 1998) at z > 0.2
• OCRA-p on Toruń 32-m (OCRA-F now
being debugged; OCRA-C possible)
• noise ~ 0.4 mJy [less than 1 hour/cluster]
AMI highly effective at this (e.g.,
Rodríguez-Gonzálvez et al. 2011,
Shimwell et al. 2011)
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The Sunyaev-Zel’dovich effect
The thermal SZ effect
Harder work in blank fields, but rewarding because of
expected linear scaling with Uthermal; e.g.,
• Planck survey (Planck collaboration 2011), 189
clusters to z = over 3  104 deg2 (ERSC)
• ACT survey (Marriage et al. 2010), 23 clusters to z =
1.07 over 455 deg2 (2008 dataset)
• SPT survey (Vanderlinde et al. 2010; Williamson et
al. 2011), 21 clusters to z =1.16 over 178 deg2 (2008
dataset), 26 high-significance clusters to z = 1.13 over
2500 deg2 (2010 dataset)
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The Sunyaev-Zel’dovich effect
The thermal SZ effect
Cluster numbers appearing in surveys are lower
than original estimates
– 8 assumptions
– optimistic assumptions about survey performance
– confusion levels on primordial CMB and source
populations
• Value of survey high – want to get to lower
cluster masses (currently see only mass
function above 3  1014 M)
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The Sunyaev-Zel’dovich effect
Source contamination
SZ effects usually
evident before
source correction –
compare cluster and
trail statistics.
Uncorrected: lose
20% of clusters.
Corrected: lose 10%
of clusters (5% of
trails).
Lancaster et al. (2011)
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The Sunyaev-Zel’dovich effect
Source contamination
Contamination also
important in sub-mm:
e.g., Bullet cluster
(Johansson et al. 2011)
– lensed sub-mm
galaxies dominate
image
Need multi-resolution
(AMI-type
interferometer) and/or
multi-frequency data.
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The Sunyaev-Zel’dovich effect
Scaling relation: flux density/X-ray kT
Low-z scaling relations consistent with expected self-similar model,
but errors large – LX and TX ranges too small (Lancaster et al. 2011)
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The Sunyaev-Zel’dovich effect
Next step: blind survey
Potential field: XMMLSS. Survey blind in
SZ, provides parallel
X-ray, lensing, IR
data.
Too far south for
Toruń: accessible to
AMiBA.
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The Sunyaev-Zel’dovich effect
Train-wreck astronomy
RXJ 1347-1145 (z = 0.45) GBT/MUSTANG, 90 GHz, 10 arcsec
resolution (Mason et al. 2010)
Left: colour = SZ; green = HST/ACS; contours = surface mass density
(Bradac et al. 2008). Right: contours= SZ; colour = X-ray (Chandra)
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The Sunyaev-Zel’dovich effect
Train-wreck astronomy
MACS 0744+3927 (z = 0.69): shock discovered with high
resolution SZ observations: GBT/MUSTANG, X-ray;
Korngut et al. (2010)
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The Sunyaev-Zel’dovich effect
Train-wreck astronomy
MACS J0717.5+3745
z = 0.548
Clearly disturbed,
shock-like substructure,
filament
What will the SZ image
look like?
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The Sunyaev-Zel’dovich effect
Train-wreck astronomy
MACS J0717.5+3745, z = 0.548, AMI image
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The Sunyaev-Zel’dovich effect
Science to come
• Cluster physics
– Now getting fast SZ follow-up of known clusters to very high redshift
(AMI, OCRA, etc., etc.)
– SZ gives linear measures of energy and mass – excellent probes of
structure formation from appropriate samples, and testing scaling
relations
– Resolving train-wreck structures – measures of thermalization of kinetic
energy and cluster formation
• Cosmology
– Structure formation and cosmological parameters from cluster counts:
need to go factor 5 – 10 below current mass limits
– Baryonic mass fraction measurements with redshift and radius (lensing)
• Other SZ observables (kinematic effect, spectral distortions,
polarization)
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