Cosmology Redshift Survey (CRS,S8) · with 1-5% accuracy in bins of dz = 0.1 up to z = 3.5 (complementary to DESI measurements in the Northern hemisphere). •QSO Lyα survey will

4MOST – 4m Multi-Object Spectroscopic Telescope

www.4MOST.eu

Cosmology Redshift Survey (CRS,S8)Johan Richard (CRAL)

Jean-Paul Kneib (EPFL)

08th May 2019

on behalf of the S8 survey members

S8 Cosmology Redshift Survey | ESO workshop, May 6-8 2019 | Johan Richard

Cosmology Redshift Survey (CRS)

• Messenger White paper: Richard et al. 2019 astro-ph/1903.02474 • Main contributors

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Johan Richard (CRAL)

Jean-Paul Kneib (EPFL)

Chris Blake (Swinburne)

Anand Raichoor (EPFL)

Johan Comparat (MPE)

Tom Shanks (Durham)

Jenny Sorce (CRAL, AIP)

Martin Sahlen(Uppsala)

Cullen Howlett(ICRAR,UWA)

Elmo Tempel(U.Tartu, AIP)

Richard McMahon (IoA)

Maciej Bilicki(Leiden)

Boudewijn Roukema (TCfA, CRAL)

Jon Loveday(U.Sussex)

Dan Pryer(U.Sussex)

Thomas Buchert (CRAL)

Cheng Zhao (EPFL)

https://arxiv.org/abs/1903.02474


Rationale

• Standard interpretation of an accelerating expansion: Dark Energy

• Standard rulers (BAO) and standard candles (SN Ia) give 1% precision on distances, and DESI + Euclid will reach < 1% in the near future.

• Complementary probe: growth of structures in the inhomogeneous Universe

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Redshift Space Distortions

!4S8 Cosmology Redshift Survey | ESO workshop, May 6-8 2019 | Johan Richard

Weak-lensing

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Need:

• ellipticities • redshift information


Combining lensing and spectroscopy

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• Lensing and spectroscopy are sensitive to theories of gravity

• Perturbations to FRW metric:

• The metric potentials , identical in GR, could differ

• Lensing / light rays receive the contribution from

• RSD / Infalling galaxies are sensitive to the potential


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Combining lensing and spectroscopy


Blake et al. 2016 Jullo et al. 2019 (z=0.6)

Reyes et al. 2010

Cosmology with 4MOST

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• 4MOST / VISTA benefits from an excellent observing site in the Southern hemisphere.

• DECAM provides the best quality of imaging to select targets, until we have access to LSST.

• Strengths: synergies with Southern facilities - cross-correlation with weak-lensing (DES and KIDS) - synergies with radio surveys (SKA and precursors) - synergies with CMB surveys

CRS will measure redshifts for 8 Million galaxies and QSOs


Primary science goal :Testing gravitational physics with overlapping lensing and spectroscopy

•CRS redshifts allow for galaxy-galaxy lensing measurements

- adds bias of lens sample - clean selection of lenses

•Mitigating RSD measurements by constraining bias •Measurements of QSO magnification bias •Calibration of photometric redshifts


Photometric redshift calibration

•Photometric redshift errors are an important systematic in weak lensing analyses

•Main parameters (mean, width) of redshift distributions have to be known in individual bins at 10-3 level

•Calibration through training sets •Calibration through photo-z / spec-z cross-correlations • Important issue for current and future lensing surveys

(DES, Euclid, LSST…)


Synergies with CMB experiments

•The Cosmology Microwave Background (CMB) contains a wealth of information about cosmic evolution through interaction with large-scale structures:

- Sunayev-Zel’dovich (SZ) effect - Integrated Sachs-Wolfe effect - Weak lensing of the CMB

•Cross-correlation with CRS redshifts will provide growth rate measurements


Auxiliary ScienceLarge-scale structure mapping:

• Structural studies of voids (Sahlen et al. 2018)

• Cosmological distance and effective expansion rate measurements with 1-5% accuracy in bins of dz = 0.1 up to z = 3.5 (complementary to DESI measurements in the Northern hemisphere).

• QSO Lyα survey will exploit its ~2 times higher spectral resolution than DESI to measure structure in the Lyα forest down to sub-Mpc scales for BAO measurements (e.g. Bautista et al., 2017).

• Tests of average curvature and effective expansion rate consistency (e.g. Clarkson et al. 2008), to test the standard hypothesis that comoving space is rigid (Roukema et al., 2015).


Auxiliary Science

Synergies with other surveys:

HI + optical spectroscopy cross-correlation ➡ evolution of the neutral hydrogen content of galaxies (Wolz et al., 2017).

Optical + X-ray imaging cross-correlation: ➡ effect of quasar feedback on clustering (e.g. Risaliti & Lusso, 2018). Together with TIDES (S10): SNe host-galaxy redshifts from LSST ➡ gravitational tests using peculiar velocities (Howlett et al., 2017). Follow up galaxy-galaxy strong lensing events found by Euclid and LSST (Collett 2015), which can be used as probes for the dark matter distribution at galactic scales.

•


Implementation: targets

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Bright Galaxies (BG) Luminous Red Galaxies (LRG)

Emission Line Galaxies (ELG) Quasars (QSO)

Science goals require suitable targets for specs over 0 < z < 3.5


0.05

Implementation: Sky Coverage

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● Survey area selected to cover the largest area with high quality imaging for photometric selection (7500 deg2) ● Photometric selection: DES/ATLAS, VHS and WISE photometry ● Main areas of sky are DES+KIDS and ATLAS ● Avoid areas overlapping with DESI at dec. > -20 ● Smaller sky area for ELGs covering KIDS-S and part of DES (1000 deg2)


Implementation: Sky Coverage


● VHS+WISE , 16 < J < 18, 250/deg2, 0.05<z<0.4 ● easy to select, almost pure sample

Color selections - BG

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(A. Raichoor)


● VHS+WISE , 18 < J < 19.5, 400/deg2, 0.4<z<0.8 ● some contamination expected from lower/higher z

Color selections - LRG

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(A. Raichoor)


● DES/ATLAS, 21<g<23.2, 1200/deg2, 0.7<z<1.1 ● 1000 deg2 in KiDS-S + DES ● expected contamination from higher-z

•

Color selections - ELG

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(A. Raichoor)


Color selections - QSO + Ly-alpha

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● DES/ATLAS+WISE ugrizW1W2 (use of NEOWISE) ● Basic selection: UV excess + IR excess

Chehade et al 2016


Selections - QSO + Ly-alpha

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● Limitation on u-band coverage (but a lot of progress, ATLAS + part of DES for QSO selection)

● QSO-Lyman-alpha will be selected from NEOWISE

● add Star / QSO separation based on variability (+ Gaia proper motion at g<20.5)


QSO completeness in %50 60 70 80 90 100

Stel

lar r

ejec

tion

in %

75

80

85

90

95

100

z>2.15 quasars

DES 5 yrs g<21DES 5 yrs g<22DES 5 yrs g<23

Courtesy: N. Palanque-Delabrouille

Redshift distributions


4FS: mock catalogues

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https://www.cosmosim.org/cms/simulations/mdpl2/


MultiDark, L=1Gpc/h (Klypin et al 2016)

+ replication (Comparat et al. 2019)

BG, LRG, QSO (Rodriguez-Torres S. et al. 2016, 2017)ELG (Favole G. et al. 2016, Guo H. et al. 2019)

+ HOD models

+ use of stacked SDSS templates + empirical magnitude distribution

(J. Comparat)

https://www.cosmosim.org/cms/simulations/mdpl2/

4FS: results


Current range : 4 MFhours required to reach 8M targets, but ~2.5 MFhours observed

4FS: results


Current range : 4 MFhours required to reach 8M targets, but ~2.5 MFhours observedTarget overlap : in particular clusters and AGN surveys in the eRosita overlap regionOptions : remove the ELG or QSO Lyman-alpha targets, reduce survey area

Summary - Next steps


• The main goal of 4MOST CRS is to combine the best quality imaging in the South (DES+KIDS, ATLAS) for lensing with spec-z to perform cross-correlations and cosmological tests.

• CRS will provide redshifts for millions of galaxies and QSO up to z=3.5 with various target selections.

• Our focus is now to improve the QSO target selection, as well as test possible options (priorities, filler targets?) to achieve the science goals.

Documents

Cosmology Redshift Survey (CRS,S8) · with 1-5% accuracy in bins of dz = 0.1 up to z = 3.5 (complementary to DESI measurements in the Northern hemisphere). •QSO Lyα survey will