The Sunyaev-Zel’dovich effect AMI day, 2011 September 30
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The Sunyaev-Zel’dovich effect
The Sunyaev-Zel’dovich effectAMI day, 2011 September 30
Mark Birkinshaw
University of Bristol
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2011 September 30 Mark Birkinshaw, U. Bristol 2
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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2011 September 30 Mark Birkinshaw, U. Bristol 3
The Sunyaev-Zel’dovich effect
The thermal SZ effect
Total SZ flux density
thermaleeRJ UdzTndS • 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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2011 September 30 Mark Birkinshaw, U. Bristol 4
The Sunyaev-Zel’dovich 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)
The thermal SZ effect
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2011 September 30 Mark Birkinshaw, U. Bristol 5
The Sunyaev-Zel’dovich 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)
The thermal SZ effect
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2011 September 30 Mark Birkinshaw, U. Bristol 6
The Sunyaev-Zel’dovich 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)
The thermal SZ effect
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2011 September 30 Mark Birkinshaw, U. Bristol 7
The Sunyaev-Zel’dovich effect
Source contaminationSZ 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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2011 September 30 Mark Birkinshaw, U. Bristol 9
The Sunyaev-Zel’dovich effect
Source contaminationContamination 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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2011 September 30 Mark Birkinshaw, U. Bristol 10
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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2011 September 30 Mark Birkinshaw, U. Bristol 11
The Sunyaev-Zel’dovich effect
Next step: blind survey
Potential field: XMM-LSS. Survey blind in SZ, provides parallel X-ray, lensing, IR data.
Too far south for Toruń: accessible to AMiBA.
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2011 September 30 Mark Birkinshaw, U. Bristol 12
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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2011 September 30 Mark Birkinshaw, U. Bristol 13
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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2011 September 30 Mark Birkinshaw, U. Bristol 14
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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2011 September 30 Mark Birkinshaw, U. Bristol 15
The Sunyaev-Zel’dovich effect
Train-wreck astronomy
MACS J0717.5+3745, z = 0.548, AMI image
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2011 September 30 Mark Birkinshaw, U. Bristol 16
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)