KiDS+VIKING: Cosmic shear tomography with optical+IR data

Hendrik Hildebrandt - Ruhr-University BochumGerman Centre for Cosmological Lensing (GCCL)

KiDS: Kilo Degree Survey DES: Dark Energy Survey

HSC: Hyper-Suprime Cam SurveyStage III SurveysVIKING

Stage III cosmic shear results

= σ 8

(Ωm

/0.3

)0.5

Hildebrandt et al. (2018)

George E.: Wrong or new physics?

2.3σ

Hildebrandt et al. (2018)

Hildebrandt et al. (2018)

Hildebrandt et al. (2018)

Hildebrandt et al. (2018)

KV450 photometric redshifts

Wright et al. (2018)Spec-z

Re-weight spec-z surveys to be more representative.

1. Magnitude space needs to be fully covered.2. Requires unique relation colour-redshift relation.

Redshift calibration with spec-z

Hildebrandt et al. (2017)

σ<z> ≈ 0.01 − 0.04

from bootstrapping

the data

cross-checked on MICE

simulations

Self-organising map of mag space

~99% coverage of 9D mag space in KV450.Wright et al. (2019)

KV450 “gold” sample

Wright et al. (2019)

~85% of the sources.

σ<z> ≈ 0.007

Spectroscopic calibration of DES-Y1

Caveat: Re-weighting done in 4D only.Joudaki et al. (2019)

0.1 0.2 0.3 0.4 0.5

≠m

0.72

0.80

0.88

0.96

S8

DES-Y1 (original n(z), KV450 setup)

DES-Y1 (KV450 setup)

Planck 2018

S8 constraints

Joudaki et al. (2019)

1.9σ tension between DES and Planck

0.1 0.2 0.3 0.4 0.5

≠m

0.7

0.8

0.9

S8

KV450

DES-Y1

KV450 + DES-Y1

Planck 2018

KV450 and DES-Y1 combined

Joudaki et al. (2019)

2.5σ tension between WL and Planck

3.2σ tension between WL and Planck

Asgari et al. submitted

KV450 cosmic shear + BOSS wedges

Tröster et al. (2019)

3.5σ tension between WL and Planck

(but only ~2.1σ over full parameter space)

Important: Sampling with ΛCDM, not geometric BAO

parameters.

Problems with the redshift calib.• Calibration with photo-z (e.g. COSMOS-2015):• Outliers => underestimate <z>• Bias => underestimate <z>

• Calibration with spec-z:• Magnitude-space coverage => underestimate <z>• Uniqueness of colour-redshift relation => underestimate <z>• Wrong spec-z => <z> drawn to the mean of all spec-z

=> We might still overestimate S8!

Summary & Outlook

• ~2-3σ tension in S8 between Planck and low-z WL measurements (KV450, DES-Y1 re-calibrated). Like H0 a few years ago?

• Are we “wrong”? Systematics? Redshift calibration?

• Other LSS probes show similar discrepancies. No S8 higher than Planck!Related to H0 crisis? Will this evolve into a serious problem for ΛCDM?

• Exciting times: KiDS+VIKING and DES finished; all 3 stage-III surveys analysing several times more data now.