Observational Cosmology (C. Porciani / K. Basu) Lecture 7 - - PowerPoint PPT Presentation

Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Course website: http://www.astro.uni-bonn.de/~kbasu/astro845.html

Lecture 7

Cosmology with galaxy clusters

(cluster astrophysics and cosmology)

Observational Cosmology

(C. Porciani / K. Basu)

Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Outline of today’s lecture

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Modeling total cluster mass Halo mass function, scaling relations Optical observation: richness, red-sequence Joint SZ/X-ray modeling APEX-SZ & ALMA

Observational Cosmology Lecture 3 (K. Basu): CMB spectrum and anisotropies

Questions?

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Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Clusters in hydro-simulations

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z=4 z=2 z=0 Dark matter Baryons Stellar distribution

Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Mass probes

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X-ray strong lensing X-ray SZE weak lensing SZE weak lensing R2500 ~ 0.3 R200 ~ 0.5 Mpc R500 ~ 0.7 R200 ~ 1 Mpc R200 ~ 1.5 Mpc

Roncarelli, Ettori et al. 2006

Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Halo mass function

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Observable Theory Press-Schechter (1974) Jenkins et al. (2001) Cosmology predicts the variance on mass scale M:

Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Measuring cluster mass

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The condition of hydrostatic equilibrium determines the balance between pressure force and gravitational force: Using equation of state for ideal gas: For isothermal beta model:

Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

HSE mass profile

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HSE mass bias Abell 2204 Abell 1689

Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Cluster virial radius

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Beware: r200 is not the same thing as virial radius! In a spherical collapse model, the behavior of a mass shell follows the equation: Under simplistic assumption (“top-hat model”, which means cluster is assumed to be of constant density), the mean density of perturbations that lead to collapse is 18π2 ≈ 178 for flat, EdS cosmology. For ΛCDM the solution is: Thus for z=0, the “virial radius” should be ~ r100 !

Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Scaling relations

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Prediction in terms of mass Detection via X-ray flux, SZ flux, optical richness dN / dz dM ➞ dN / dz dF

Prediction in terms of mass Detection via X-ray flux, SZ flux, optical richness dN / dz dM ➞ dN / dz dF

Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Scaling relations

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Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Self-similar scaling

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The simplest model to explain the physics of the ICM is based on the assumption that only gravity determines its properties. This makes clusters a scaled version of each other. For hydrostatic equilibrium:

Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

M-T scaling relation

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Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

M-L and L-T relations

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Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

M-L and L-T relations

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238 clusters, z < 0.5 (XLF), including systematics

Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Results for cosmology

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Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Results for cosmology

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Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Future constraints

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Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Clusters in optical / near-IR

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Clusters in optical surveys are selected on the basis of richness, which depends on the number of galaxies observed within a certain projected radius from the cluster center. Yee & Ellingson 2003

Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Identifying cluster galaxies

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• Spectroscopic redshifts: Most galaxies do not have

spectra taken

• Photometric redshifts: Δz ~ 0.03, in clusters, require

Δz ~ 0.003 (vel. ~ 900 km/s)

• Red-sequence colors: Uncertainties ~ 0.03, ridgeline

width ~ 0.06 If the photo-z is obtained from colors, how can red-sequence color do better than photo-z?

Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Cluster red sequence (CRS)

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The CRS method is motivated by the fact that all rich clusters have a population of early type galaxies that follow a strict color-magnitude

• relation. The color of the red-sequence is dependent on the cluster
• redshift. This means that the color can be used to estimate the redshift of

the cluster. z = 1.62

Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Velocity dispersion

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Velocity dispersion is the optical analog of X-rat temperature. Observationally: σ2 = (1.0 ± 0.1) kB Tlum / μ mp But this gas-mass weighted temperature, Tlum, is typically ~20% higher than X-ray spectroscopic temperature (non-gravitational efgects? clumping?)

Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Measuring velocity dispersion

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Persistence of substructures (simulations by White, Cohn & Smit 2010) The velocity field traces the filamentary substructure

While the thermal gas emitting in X-rays is present in all clusters, the detection of extended radio emission only in ~10% of the systems indicates that the non-thermal plasma is not a common property of galaxy clusters. Non-thermal emissions over ~1 Mpc scales are present only in the most massive merging systems.

Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Radio observation of clusters

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327 MHz map of the mini-halo in the Perseus cluster (z = 0.018).

Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Clusters detected by APEX-SZ

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• 12-m on-axis ALMA prototype
• Located at the Chilean altiplano,

elevation 5100 m

• 1 arcmin reolution @ 150 GHz, 0.4 deg

FoV

• Surface accuracy 18 μm

Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

APEX telescope

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• PI instrument on APEX, commissioned Spring 2007,

approx 600 hours of data

• Demonstrates new technologies for SZ experiments:
• TES bolometers
• Multiplexed readout electronics
• Pulse tube cooler (no cryogen loss)
• Can track sources in RA-Dec, powerful camera for

targeted cluster observation

Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

APEX-SZ instrument

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Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Joint SZ/X-ray modeling

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Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Density and temperature profiles

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J0717.5+3745 at z = 0.548 Clearly disturbed, shock-like substructure,

• filament. What will SZ image look like?

Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Mergers, shocks and bubbles

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Perseus cluster Abell 2052

Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters

Future: SZ imaging with ALMA

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