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 2011 September 30Mark Birkinshaw, U. Bristol2 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, y e, the dimensionless electron temperature weighted by the scattering optical depth.

The Sunyaev-Zel’dovich effect 2011 September 30Mark Birkinshaw, U. Bristol3 The thermal SZ effect Total SZ flux density 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

The Sunyaev-Zel’dovich effect 2011 September 30Mark Birkinshaw, U. Bristol4 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-L X 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

The Sunyaev-Zel’dovich effect 2011 September 30Mark Birkinshaw, U. Bristol5 Harder work in blank fields, but rewarding because of expected linear scaling with U thermal ; e.g., Planck survey (Planck collaboration 2011), 189 clusters to z = over 3  10 4 deg 2 (ERSC) ACT survey (Marriage et al. 2010), 23 clusters to z = 1.07 over 455 deg 2 (2008 dataset) SPT survey (Vanderlinde et al. 2010; Williamson et al. 2011), 21 clusters to z =1.16 over 178 deg 2 (2008 dataset), 26 high-significance clusters to z = 1.13 over 2500 deg 2 (2010 dataset) The thermal SZ effect

The Sunyaev-Zel’dovich effect 2011 September 30Mark Birkinshaw, U. Bristol6 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  M  ) The thermal SZ effect

The Sunyaev-Zel’dovich effect 2011 September 30Mark Birkinshaw, U. Bristol7 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)

The Sunyaev-Zel’dovich effect 2011 September 30Mark Birkinshaw, U. Bristol8 Source contamination Bullet cluster, LABOCA (extensively filtered). High-frequency structure affected by bright point source Many other point sources; SZ effect also detected – easier in other bands, but not in the north! (Lopez-Cruz et al.)

The Sunyaev-Zel’dovich effect 2011 September 30Mark Birkinshaw, U. Bristol9 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.

The Sunyaev-Zel’dovich effect 2011 September 30Mark Birkinshaw, U. Bristol10 Scaling relation: flux density/X-ray kT Low-z scaling relations consistent with expected self-similar model, but errors large – L X and T X ranges too small (Lancaster et al. 2011)

The Sunyaev-Zel’dovich effect 2011 September 30Mark Birkinshaw, U. Bristol11 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.

The Sunyaev-Zel’dovich effect 2011 September 30Mark Birkinshaw, U. Bristol12 Train-wreck astronomy RXJ (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)

The Sunyaev-Zel’dovich effect 2011 September 30Mark Birkinshaw, U. Bristol13 Train-wreck astronomy MACS (z = 0.69): shock discovered with high resolution SZ observations: GBT/MUSTANG, X-ray; Korngut et al. (2010)

The Sunyaev-Zel’dovich effect 2011 September 30Mark Birkinshaw, U. Bristol14 Train-wreck astronomy MACS J z = Clearly disturbed, shock-like substructure, filament What will the SZ image look like?

The Sunyaev-Zel’dovich effect 2011 September 30Mark Birkinshaw, U. Bristol15 Train-wreck astronomy MACS J , z = 0.548, AMI image

The Sunyaev-Zel’dovich effect 2011 September 30Mark Birkinshaw, U. Bristol16 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)