hans böhringer - eso

Hans Böhringer ESO 4MOST workshop 7. 5. 2019

4MOST Survey for Euclid Galaxy Clusters

ESO 4MOST workshop 7. 5. 2019

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Hans BöhringerUniversity Observatory München

On behalf of the Euclid Galaxy Cluster Working Group

Involving: Fabio Bellagamba, Andrea Biviano, Stefano Borgani, Florence Durret, Lauro Moscardini, Matteo Maturi, Mario Radovich,

Mauro Roncarelli, Piero Rosati

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Euclid Survey Mission Mapping the Geometry of the Universe

Most important and most promising cosmology mission after Planck !

Nominal space mission: 5 yr sky survey: 15 000 deg2 (40 deg2 deep) -  Optical (550 -900 nm) m < 24.5 (0.1 arcsec) Y, J, H m<24 (0.3 arcsec)-  + NIR spectroscopy (1100 – 2000 nm)

Goal: probing dynamical Dark Energy, modified Gravity, nature of Dark Matter + lot of astronomical legacy science !!

Primary cosmological probes: Gravitational lensing & Galaxy Clustering

Important additional probe, galaxy clusters: number counts and spatial correlation as function of z (up to z = 2)

Euclid mission starting: 2022

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Galaxy Clusters an Independent and Complementary Probe

Constraints for the parameters of dynamical dark Energy : w(a) = wp + (ap – a)wa

Euclid all Euclid all + Planck

Clusters are an important complement to the primary probes – in particular also for the determination of the neutrino masses (with Δmν ~ 0.02 eV) !

Euclid Red Book 2011

+ clusters

Figure of merit : 1/(Δwp x Δwa)

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Euclid Cluster Detections

Euclid cluster detections (in 15 000 deg2):

200 000 clusters (S/N > 5)2 Million (S/N > 3) 80% compl.

Mass limit ~ 8 1013 Msun (S/&N > 3)

Euclid will provide WL shear maps à“unbiased” mass estimates for the clusters. (most important advance for cluster cosmology !)

mass limit

Sartoris et al. 2016

S/N > 5

S/N > 3

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Why Spectroscopic Redshifts ?

From Euclid we will get spectroscopic redshifts for massive clusters (Hα for SF galaxies) with z > 0.8 from NIR spectroscopy.Important and less explored redshift range z = 0.4 to 0.8: mostly photometric redshifts. Having spectroscopy would add:

-  precise distances (accurate physical properties, e.g. mass)

-  velocity dispersions as additional mass proxy

-  accurate positions for correlation analysis

-  important information for galaxy evolution studies

-  evaluation and calibration of the photometric cluster finder -  à crucial to obtain proper cluster selection function, essential for

precise cosmological results

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Two Step Approach of the Project

Follow-up of Euclid detected clusters is only possible in the second half of the survey.

A)  Follow-up of the clusters detected in the KIDS/VIKING Survey with the officially selected Euclid Cluster Finders (AMICO & PZWav) in 1400 deg2

B)  Follow-up of the clusters detected in the Euclid survey (~ 3000 deg2)

Mains Goals:

•  Precise characterisation of the EUCLID cluster selection function

•  Additional mass calibration

•  Astrophysics of galaxy cluster evolution with an unprecedented data set

KIDS mag. limits u = 24.8 g = 25.4 r = 25.4 i = 24.2 VIKING z = 23.1 Y = 22.3 J = 22.1 H = 21.5 K = 21.2

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Euclid Cluster finder AMICO applied to the KIDS survey

Maturi et al. 2019Bellagamba et al. 2018, 19

Adaptive Matched Identifier of Clustered Objects: MF(α, δ, mr, p(z)) à probab. for each gal.

Assignment probability is color coded

7988 clusters in 438 (used 377) deg2 of DR3 KIDS- 18 cluster per deg2

Weak lensing mass calibration

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AMICO Cluster Detections

Maturi et al. 2019Bellagamba et al. 2019

Completeness and Purity of the cluster sample (purity of ~95% from mock simulations)

~ 1014 Msun clusters

redshift accuracy Δz/(1+z) ~ 0.02

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4MOST Target Statistics for z = 0.5 – 0.6377 deg2 DR3-KIDS, mr < 22, probability limit = 0.2

spectroscopic targets cluster members

Almost all clusters with M200 > 1014 Msun have more than 10 member galaxy redshifts, the most massive clusters are dynamically very well characterised.Most important is the overall statistics: ~ 25 000 galaxy redshifts for about 1400 clusters à characterisation on the percent level.

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4MOST Target Statistics for z = 0.7 – 0.8

Most clusters with M200 > 3 1014 Msun have more than 10 redshifts, most other clusters have more than 3 redshifts which allows statistical stacking. à reliable redshifts for clusters, some dynamical information from stacking

spectroscopic targets cluster members

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Summary of the Target Statistics for the KIDS/VIKING and Euclid Follow-up

Extrapolated to full KIDS/VIKING follow-up:

~ 1.2 Million targets above z = 0.1

mr < 20 - 21 for z > 0.4 ~ 500 000 targetsmr < 22 for z > 0.4 ~ 500 000 targets

This includes:•  additional targets detected by PZWav•  exploration of ~ 4000 lower S/N cluster detections (@ z > 0.4)•  exploration of the lower probability regime, 100 000 targets “à To better understand the sample and richness completeness

Extrapolation to Euclid Survey follow-up:

We hope to explore a region of up to 3000 deg2, thus we expect to have about twice as many targets

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Fibre Allocation Feasibility

Studying target density in the clusters: 4MOST would allow us to target most of theselected galaxies (@ z > 0.4) in two 1 hr visits – apart from central cluster regions in the redshift range 0.4 – 0.6, where we would have a loss of 50 % in the worst case, if there is no other survey. To account for other surveys we assume pessimistically that we will obtain spectra only for 20 – 40% of our selection. This gives the following target statistics:

1400deg2 alltargets 20–40% memberspectra

total 1200k 240–480k 120–240k

z>0.4 500k 100–200k 50–100k

z<0.4 500k 100–200k 50–100k

extratargets 200k 40–80k 10–30k

z=0.5–0.6 150k 30–60k 15–30k

z=0.7–0.8 12k 2.4–4.8k 1.2–2.4k

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Science Prospects

Statistical precision for main project goals [pessimistic (optimistic)]:

z = 0.5 – 0.6 z = 0-7 – 0.8selection function: - 3 bins of probability:: 1.5 (1) % 5 (3.5) % - 4 bins mag., 5 bins prob.: 3.7 (2.6) % 12 (9) %

mass calibration: 10 mass bins: 2.5 (1.8) % 9 (6) % 5 mass bins: 1.8 (1.3) % 6 (4.5) % overall < 1% 2.9 (2) %

cluster astrophysics 10 mass bins 3000 – 6000 galaxies 5 mass bins 240 – 480 galaxies

à Precision assessment at ~1 % level for z <= 0.6 and few % above. We can reach our mail goals !

With the Euclid follow-up these numbers will increase by factor 2

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Synergy/Overlap with consortium surveys: eROSITA Clusters - Waves

eROSITA

eROSITA finds more groups and clusters at redshifts < 0.4 (40 000 groups and clusters down to 1013 Msun) , Euclid has many clusters at high redshift.

Waves is also targeting the KIDS/VIKING survey regions. Here the main interest is the evolution of structure (dark matter halos down to 1011 Msun,filaments and voids to redshift of z = 0.2 in WAVES wide).

0.9 Million galaxies Z >= 21.1 to photoz = 0.2

The study of galaxy clusters in the redshift range z = 0.4 to 0.8 with high precision (excellent statistics) is the special field for the 4MOST follow-up of Euclid and KIDS/VIKING.Thus there is a good synergy with the other two surveys!

eROSTA White Book

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Conclusions

•  We propose to make an important contribution to enhance the Euclid cosmology and cluster science results.

•  There is an optimised survey strategy and clear goals to achieve this.

•  The Euclid cluster selection function and cluster masses will be calibrated at the (few) percent level.

•  There will be an unprecedented sample of galaxy spectra of cluster members to study cluster evolution in many aspects at z = 0.4 to 0.8

•  The requirements are: <~ 500 000 galaxy spectra for Stage I (Test on KIDS/VIKING region) <~ 1 Mill. galaxy spectra for Stage II (Euclid follow-up)