Measuring the kinematic Sunyaev Zel’dovich Effect

with SPT and DES

Moriond   March  24,  2016

Kyle  Story   Stanford  University   KIPAC

Measuring the kinematic Sunyaev Zel’dovich Effect

with SPT and DES

In  collabora@on  with:   B.  Soergel,  S.  Flender,  L.  Bleem,  T.  Giannantonio,  G.  Efstathiou,     as  well  as  the  SPT  and  the  DES  collabora@ons

arXiv:  1603.03904

The South Pole Telescope Collaboration

The Dark Energy Survey Collaboration

The South Pole Telescope (SPT) 10-meter primary dish, observe the CMB with arcminute resolution SPT-SZ (2007) 960 detectors 95,150,220 GHz

SPTpol (2012) 1600 detectors 95,150 GHz +Polarization

SPT-3G (2017) ~16,000 detectors 95,150,220 GHz +Polarization Kyle Story

Recall talk by Amy Bender

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Slide from T. Giannantonio

Slide from B. Benson

CMB + galaxy surveys: Powerful playground for testing the consistency of cosmology and probing open questions.

CMB Last-Scattering Surface “back-light” on the rest of the universe Recall talk by Nabila Aghanim

• • • •

CMB lensing Galaxies Galaxy weak lensing kSZ (image modified from WMAP/NASA)

Primer: the thermal SZ effect The Sunyaev-Zel’dovich effect is caused by CMB photons inverse Compton scattering off of electrons in hot intra-cluster gas. CMB illuminates galaxy clusters from behind: “back light”

Kyle Story

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If the cluster is moving with respect to the CMB rest frame, the spectrum will contain an additional Doppler shift.

(Carlstrom 2002)

thermal SZ

kinematic SZ

Sunyaev & Zel’dovich 1980 Kyle Story

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Why is the kSZ signal interesting? The kSZ probes the cosmic velocity field on ~100 Mpc scales electron line-of-sight velocity electron number density

Using  the  kSZ,  we  can  study: •  “Missing  Baryon”  problem   •  Probe  of  Large  Scale  Structure   •  Probe    of  cluster  physics   (electron  density)   •  Probe  of  gravity  on  ~100  Mpc   scales Kyle Story

Local  cosmic  velocity  field  (Courtois  et.  al.  2013)

How do we measure the kSZ? 90

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Angular Scale 5′ 2′

10′

Planck

SPT 220 GHz

SPT - S13

SPT 150 GHz

ACT 148 GHz ACT 220 GHz

SPT 95 GHz

Power

1000

1′

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Angular Scale

2500

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thermal SZ

kinematic SZ

The SZe contributes to the CMB anisotropy power spectrum. • tSZ component is well measured (e.g., George et al 2015) • kSZ component is very small! ApJ 779 (2013), arXiv:1210.7231 (KTS et al.) ApJ 799 (2015), arXiv:1408.3161 (George, … KTS et al.)

Kyle Story

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arXiv:1511.02843 (Flender et al.)

There is another way to detect the kSZ: the pairwise estimator Pairwise Estimator:

where

(Ferreira 99)

Key Concept: On average, clusters move towards each other under their mutual gravitational attraction. Method: subtract CMB temperatures at the location of pairs of galaxy clusters. Kyle Story

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Figure credit: T. Giannantonio

There is another way to detect the kSZ: the pairwise estimator Pairwise Estimator:

where

(Ferreira 99) First measurement: ACT + BOSS (spec-z) (Hand et al. 2012)

Probes a combination of cluster physics and cosmology:

where b: cluster bias, τ: cluster optical depth, f: growth rate, σ8: normalization of matter power spectrum

~3σ (PTE 0.2%)

Kyle Story

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Figure credit: T. Giannantonio

Analytic template for the pairwise kSZ (B. Soergel) Pairwise kSZ probes mass-weighted mean pairwise velocity v12(r)

(Keisler & Schmidt 2012, Schmidt 2010)

b: mass-weighted mean bias ξδv : density-velocity correlation function, ξ : density auto-correlation function

Pairwise kSZ amplitude:

In linear regime:

arXiv:1603.03904 (Soergel, Flender, KTS et al.)

Slide from B. Soergel

Ingredients to the pairwise kSZ estimator:

2h

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-40° -50° -60°

Catalog of clusters from DES

Kyle Story

CMB temperatures from SPT

DES Y1 Cluster Catalog: redMaPPer

(E. Rozo, E. Rykoff)

•  redMaPPer  Y1  mask:  ~1,200  deg2   •~6,700  clusters  with  N>20  gal.   •  Photoz:  σz/(1+z)  ~  0.010  -­‐  0.015

Number of gal. in each cluster Kyle Story

Redshift uncertainties arXiv:1603.03904 (Soergel, Flender, KTS et al.)

SPT CMB Temperature data

~10°

Apply a matched filter to the CMB data. • The filter is a combination of the expected cluster profile and the instrumental beam. • This filter is convolved with the CMB map • Each pixel in the filtered map is the amplitude of the best-fit profile centered at that pixel.

Unfiltered CMB map Kyle Story

Filtered map

Haehnelt & Tegmark 96

Results: 4.2σ detection! First pairwise detection with photo-z’s

Pairwise Estimator:

where

• • •

DES redMaPPer clusters 6,700 clusters (20 < Ngal < 60) SPT Temperature data

arXiv:1603.03904 (Soergel, Flender, KTS et al.) Kyle Story

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Null Tests all pass

arXiv:1603.03904 (Soergel, Flender, KTS et al.) Kyle Story

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We validate our analysis method and study systematics effects using simulations. (S. Flender)

• Full-sky lightcone out to z~1 from N-body simulations.

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• Gas prescription for hot intra cluster gas • account for astrophysical affects (star formation, feedback , non-thermal pressure) -8 300

100

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-100

arXiv:1511.02843 (Flender et al.) Kyle Story

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Studying Systematics with simulations

Redshift (photo-z) uncertainty reduces the signal at low separations, but the fit remains unbiased.

Contamination from primary CMB and tSZ does not bias results

arXiv:1603.03904 (Soergel, Flender, KTS et al.) Kyle Story

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Studying Systematics with simulations

Redshift (photo-z) uncertainty reduces the signal at low separations, but the fit remains unbiased.

Contamination from primary CMB and tSZ does not bias results

arXiv:1603.03904 (Soergel, Flender, KTS et al.) Kyle Story

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Studying Systematics with simulations

Redshift (photo-z) uncertainty reduces the signal at low separations, but the fit remains unbiased.

Contamination from primary CMB and tSZ does not bias results

arXiv:1603.03904 (Soergel, Flender, KTS et al.) Kyle Story

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kSZ measurements are in the regime of “first detections.” Measurements to date: Pairwise Estimator: 1. ACT x BOSS (spec-z), Hand et al. 2012: PTE = 0.002 (X σ) (rejection of null hypothesis) 2. Planck x SDSS-DR7 CGC (spec-z), Planck Int XXXVII 2015: 1.8 - 2.5 σ 3. SPT-SZ x DES-Y1 (photo-z), Soergel et al. 2016: 4.2 σ (template fit)

Other Estimators: 1. Planck x SDSS-DR7 CGC (spec-z), Planck Int XXXVII 2015: 3.0 - 3.7 σ (cross-corr with velocity reconstruction) 2. ACTpol x BOSS (spec-z), Schaan et al. 2015: 2.9 - 3.3 σ (stack on velocity reconstruction) 3. Planck, WMAP x WISE (photo-z), Hill et al. 2016: 3.8 - 4.5 σ (T^2 cross LSS) Kyle Story

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Future kSZ measurements will be high S/N. Challenging interpretation, but large potential payoff. 4.2σ detection (statistical significance) of the kSZ from DES clusters and SPT CMB data (first detection from photometric data) Systematics limiting the interpretation: • redshift uncertainties • mis-centering of clusters • cluster profile • theory (halo bias, velocity model) • tSZ contamination • astrophysics (constrain τ and b, measure f?)

S/N Projections for future surveys

tSZ and foregrounds completely removed

arXiv:1603.03904 (Soergel, Flender, KTS et al.) Kyle Story

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arXiv:1511.02843 (Flender et al. 2015)

Thanks for listening!