Towards the first detection using SPT polarisation CMB cluster lensing Towards the first detection using SPT polarisation ASA 2016 meeting, Sydney 04. 07. 2016 Srinivasan Raghunathan School of Physics University of Melbourne

In a nutshell … South Pole Telescope – Observes CMB (both T, and P). Identifies galaxy clusters using tSZ effect. Observed CMB is lensed due to the LSS and galaxy clusters. Lensed CMB is important to extract cosmological information. Optimal estimators can reconstruct the cluster profiles using the lensed CMB –> mass estimator. CMB cluster lensing using temperature data reported by SPT-SZ. This work – aimed towards the first detection of CMBpol cluster lensing.

Cosmic Microwave Background Remnant radiation from the Big-Bang. Discovered by Arno Penzias and Robert Wilson – Bell Labs in 1964. Extremely homogenous and isotropic; Very close to black-body ≈ 2.7K; ∆T/T ≈ 10-5.

South Pole Telescope - Polarisation 10 meters @ South Pole. Surveys: SPT – SZ (2007 - 2011) SPTpol (2012 – 2016) SPT-3G (2017 - ) Beam: 1.2 arcmin (approximately) Gaussian. Background: Planck 143 GHz polarisation intensity map - 2015 Operating frequency: 95, 150, (and 220 for SPT-SZ) GHz. 500 sq. deg field with noise levels = 5.5, 7.7 uk-arcmin for T and P at 150 GHz.

South Pole Telescope – Galaxy clusters Free streaming CMB photons from the lss Thermal SZ effect Hot gas – presence of free electrons Galaxy cluster in the LOS No change in the CMB spectrum Shifts the CMB frequency CMB photons: < 220 Ghz = 220 GHz = Null > 220 GHz = Cluster detection using matched filter Close to 500 clusters; 25 per cent with redshift info. (Bleem et al. in preparation) Observed by the SPTpol. Temperature map - preliminary

CMB cluster lensing serve as a mass calibrator CMB lensing CMB lensed by the large-scale structures and by individual galaxy clusters. Lensing contains info. about neutrinos and D.E. Also useful for inflationary physics. Expected distortions: 1 arcmin for a massive high redshift cluster Proportional to mass of the galaxy cluster CMB cluster lensing serve as a mass calibrator Look at Anthony D.’s poster #2 for other mass proxies Not a single cluster but averaged over the entire cluster sample

CMB cluster lensing -∇y ɸ -∇x ɸ CMB lensed by the large-scale structures and by individual galaxy clusters. Kappa map -∇y ɸ -∇x ɸ Cluster: Mass = 2 x 1014 solar mass Concentration c = 3.0 redshift z = 0.6

? CMB cluster lensing -∇y ɸ -∇x ɸ CMB lensed by the large-scale structures and by individual galaxy clusters. The grav. potential can be reconstructed using modified quadratic - estimators. ? Kappa map -∇y ɸ -∇x ɸ Goal: Reconstruct kappa map from the lensed CMB – QE estimator.

CMB cluster lensing – Quadratic estimator Refer: Hu et al. 2007; arXiv:astro-ph/0701276 Gradient field Lensed field Six estimators: X = T, E Y = T, E, B TT estimator stacking 1000 clusters for different experiments Redshift information is not required.

CMB “galaxy” lensing – Quadratic estimator First detection using ACTPol experiment Madhavacheril et al. 2015 - arXiv:1411.7999. Combining measurements from CMB around 12,000 CMASS galaxies from SDSS-III/BOSS. Detection significance: 3.2 sigma. Inferred mass M200 = 1013 solar mass. TT estimator – Reconstructed kappa map

CMB cluster lensing - ML approach Template fitting: Refer: Baxter et al. 2015; arXiv:1412.7521 d – 14 x 14 arcmin cutouts of SPTpol maps centered on various galaxy clusters.

CMB cluster lensing - ML approach Template fitting: Refer: Baxter et al. 2015; arXiv:1412.7521 From data CCMB – signal covariance matrix: computed using 30,000 simulations <sT s> Generate unlensed CMB. Lens the CMB with different cluster masses and look for the increase in likelihood. Redhshift obtained by xcorr with other surveys. Combine likelihood for various clusters.

CMB cluster lensing First CMB cluster lensing detection using SPT-SZ data arXiv:1412.7521. Combining measurements from 513 clusters at mean z = 0.55 (0.14 < z < 1.25). Detection significance: 3.1 sigma. Cluster mass M200= 5.1+/-2.5 x 1014 solar mass. Mass estimate biased for high mass clusters due to cluster tSZ emission. No tSZ contamination for polarisation estimators. Mention about linear combination of 3 frequencies to remove tSZ signals. 220 GHz not available for SPTpol.

CMB cluster lensing – current status Noiseless simulations 8 different pipeline runs after combining likelihood values of 10 clusters. Excepted likelihood peak values. Null test – no lensing – Likelihood correctly peaks near zero. T Q U

(Immediate) next steps + Summary SPTpol has identified close to 500 clusters in 500 sq. deg. field. CMB is lensed by galaxy clusters and the signal can be used as a mass proxy. 3.1 sigma detection using temperature was reported by SPT-SZ in 2015. We expect >2.5 sigma detection for polarisation. Handling systematics: NFW profile, lensing due to LSS, cluster mis-centering, insufficient redshift information, beam ellipticites, T to P leakage. More clusters + redshifts: Dark Energy Survey. Improved quadratic estimator.