Galaxy Cluster Cosmology:Enhancing Upcoming Surveys

Adam Mantz (KIPAC)

Cosmic Visions Dark Energy

November 13, 2015

Outline

1. Cluster cosmology overview

2. Where things stand

3. Upcoming surveys

4. Data that can magnify the impact of upcoming surveys

What are clusters of galaxies?

Galaxy cluster: a very massive, bound collection of dark matter,ionized gas, and galaxies (M >∼ 1014M, kT >∼ 1 keV).

What do clusters do for cosmology?

I Mass function ← growth of structure, expansion, neutrino mass

I Gas-mass fractions (standard quantity) ← cosmic expansion and Ωm

I Clustering of clusters ← growth of structure, expansion

I X-ray and mm pressure measurements ← cosmic expansion

I Bulk flows ← growth of structure, expansion

I Merger statistics ← dark matter cross section

I Internal structure ← dark matter, gravity

I . . .

What do clusters do for cosmology?

I Mass function ← growth of structure, expansion, neutrino mass

I Gas-mass fractions (standard quantity) ← cosmic expansion and Ωm

I Clustering of clusters ← growth of structure, expansion

I X-ray and mm pressure measurements ← cosmic expansion

I Bulk flows ← growth of structure, expansion

I Merger statistics ← dark matter cross section

I Internal structure ← dark matter, gravity

I . . .

How it works

Three preferred survey strategies (increasing wavelength order):

I X-ray: emission from hot intracluster medium (ICM)

I optical/IR: cluster galaxies and lensed background galaxies

I mm: SZ effect (CMB spectral distortion) due to ICM

How it works

Three preferred survey strategies (increasing wavelength order):

I X-ray: emission from hot intracluster medium (ICM)→ Most massive clusters to high z, groups at lower z

I optical/IR: cluster galaxies and lensed background galaxies→ High completeness to low masses

I mm: SZ effect (CMB spectral distortion) due to ICM→ Massive clusters at any redshift

redshift

M50

0 (10

14 M

)

RASSSPTSDSS

0.02 0.05 0.10 0.20 0.50 1.00 2.00

12

510

20

Ingredients1. Predicted halo mass function from simulations

2. Observed number of clusters as a function of z and survey signal

3. Stochastic relation between mass and observable signal(s)I More astrophysics-dependent than mass functionI Data driven modeling – need to measure massesI No mass proxy is simultaneously accurate and precise!

Accuracy: weak lensing Precision: gas mass, temperature

M500 (1014 M )

Mga

s (1

013 M

)

2 5 10 20

510

20

Ingredients1. Predicted halo mass function from simulations

2. Observed number of clusters as a function of z and survey signal

3. Stochastic relation between mass and observable signal(s)I More astrophysics-dependent than mass functionI Data driven modeling – need to measure massesI No mass proxy is simultaneously accurate and precise!

Accuracy: weak lensing Precision: gas mass, temperature

M500 (1014 M )

Mga

s (1

013 M

)

2 5 10 20

510

20

Current status(from your local Stanford group)

Combining:

1. ROSAT All-Sky X-ray survey2. Weighing the Giants weak lensing3. Chandra X-ray mass proxies

4. fgas expansion data

M500 (1014 M )

Mga

s (1

013 M

)

2 5 10 20

510

20

0.0 0.2 0.4 0.6 0.8 1.0

0.06

0.10

0.14

0.18

redshift

f gas

(0.8

< r

r 250

0 <

1.2)

ΛCDMOCDMw = − 3

Current status

constant-w models

Ωm

w

ClustersCMBSNIaBAOAll

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

−2.

5−

2.0

−1.

5−

1.0

−0.

50.

0

Clusters alone:

Ωm = 0.261± 0.031

σ8 = 0.831± 0.036

w = −0.98± 0.15

growth index (modified gravity) models

0.4 0.6 0.8 1.0 1.2 1.4 1.6

−0.

50.

00.

51.

01.

52.

02.

5

σ8γ

ClustersCMBGalaxies

Clusters alone:

Ωm = 0.257± 0.030

σ8 = 0.833± 0.048

γ − 0.55 = −0.07± 0.19

Current status

Ωm

σ 8

200820102015

0.0 0.1 0.2 0.3 0.4 0.5

0.6

0.7

0.8

0.9

1.0

1.1

0.1 0.2 0.3 0.4 0.5

0.7

0.8

0.9

1.0

1.1

Ωm

σ 8

RASS + WtGRASS + WtG + fgas

RASS + WtG + fgas + XMP

I Improvement has been rapid

I Significant gains to be had from both improving absolute masscalibration (accuracy) and obtaining precise relative masses (precision).

The road ahead for big cluster surveys

2016 2017 2018 2019 2020 2021 2022 2023DESAdvACTSPT-3GeROSITAEuclidCMB-S4LSST

2024 2025 2026 2027 2028 2029 2030 2031EuclidCMB-S4LSST

. . . lots!

What other data would we like?

I (Simulations for mass function and lensing systematics)

I Confirmation and photo-z’s at high redshifts

I Absolute mass calibration at high redshifts

I Relative mass calibration (mass proxies for new detections)

I Even more surveys?

Proper forecasts of their impacts are high on the to do list. . .

What other data would we like?

I (Simulations for mass function and lensing systematics)

I Confirmation and photo-z’s at high redshifts

I Absolute mass calibration at high redshifts

I Relative mass calibration (mass proxies for new detections)

I Even more surveys?

Proper forecasts of their impacts are high on the to do list. . .

NIR imaging

I Confirmation and photo-z’s at high redshifts

I Galaxy-cluster lensing (absolute masses) at high redshifts?

Need continuing access to large ground-based and space-based facilities(e.g. VLT, Magellan, Keck, TMT/GMT, Spitzer, Hershel, WFIRST, . . . )

Spectroscopy

I Photo-z training sets for faint galaxies behind and in clusters

I Impacts cluster finding and (especially) mass calibration

Need continuing access to ground- and space-based facilities, plus futureprojects like DESI, HSC-PFS (, SPHEREx?)

X-ray imaging spectroscopy

I Provides precise relative mass calibration

I Constrains mis-centering/projection systematics(lensing and optical cluster-finding)

Current facilities: Chandra, XMM-NewtonUpcoming missions:

I eROSITA (2016 launch; 4 yr survey followed by pointed observations)

I ATHENA (2028 launch; 30 Ms survey + pointed observations)

mm observations

I Best survey for finding clusters at the highest redshifts

I CMB-cluster lensing (high-z absolute mass calibration)

Upcoming project:

I CMB Stage-4: survey combining multiple ground-based sites

CMB-cluster lensing

I Recent ∼ 3σ stacked detections by ACT and SPT.

I Potentially a great resource for absolute mass calibration athigh z, but more work needed to understand systematics.

ACT: stacked on 12,000 galaxiesMadhavacheril+ 2015

SPT: stacked on 500 clustersBaxter+ 2015

CMB-cluster lensing

I Long-term, polarization signals are more sensitive due to being lesscontaminated by primary CMB and the SZ effect

I Even so, the Stage 4 survey is not quite as deep as one would like

I Case for a dedicated camera and deep cluster observations? TBD

Hu+ 2007

Summary

I Clusters provide tight cosmological constraints, and are one of themain probes enabled by large stage 4 surveys.

I Targeted investment in supporting observations can significantlyenhance the science return of these new cluster catalogs.

I Much of what we’d like to do is completely straightforward, but thereare also some exciting new avenues.