Observational Cosmology (C. Porciani / K. Basu) Lecture 7 Cosmology with galaxy clusters (cluster astrophysics and cosmology) Course website: http://www.astro.uni-bonn.de/~kbasu/astro845.html Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Outline of today’s lecture Modeling total cluster mass Halo mass function, scaling relations Optical observation: richness, red-sequence Joint SZ/X-ray modeling APEX-SZ & ALMA 2 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Questions? 3 Observational Cosmology Lecture 3 (K. Basu): CMB spectrum and anisotropies
Clusters in hydro-simulations Dark matter Baryons Stellar distribution z=4 z=2 z=0 4 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Mass probes X-ray X-ray SZE SZE strong lensing weak lensing weak lensing Roncarelli, Ettori et al. 2006 R 2500 R 500 R 200 ~ 0.3 R 200 ~ 0.7 R 200 ~ 1.5 Mpc ~ 0.5 Mpc ~ 1 Mpc 5 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Halo mass function Observable Theory Press-Schechter (1974) Jenkins et al. (2001) Cosmology predicts the variance on mass scale M: 6 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Measuring cluster mass 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: 7 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
HSE mass profile Abell 2204 Abell 1689 HSE mass bias 8 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Cluster virial radius Beware: r 200 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 18 π 2 ≈ 178 for flat, EdS cosmology. For Λ CDM the solution is: Thus for z=0, the “virial radius” should be ~ r 100 ! 9 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Scaling relations Prediction in terms of mass Detection via X-ray flux, SZ flux, optical richness dN / dz dM ➞ dN / dz dF 10 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Scaling relations Prediction in terms of mass Detection via X-ray flux, SZ flux, optical richness dN / dz dM ➞ dN / dz dF 11 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Self-similar scaling 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: 12 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
M-T scaling relation 13 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
M-L and L-T relations 14 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
M-L and L-T relations 15 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Results for cosmology Mantz, Allen, Ebeling et al. 238 clusters, z < 0.5 (XLF), including systematics 16 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Results for cosmology Mantz, Allen, Ebeling et al. 17 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Future constraints 18 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Clusters in optical / near-IR 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 19 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Identifying cluster galaxies • Spectroscopic redshifts: Most galaxies do not have spectra taken • Photometric redshifts: Δ z ~ 0.03, in clusters, require Δ z ~ 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? 20 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Cluster red sequence (CRS) 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 21 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Velocity dispersion Velocity dispersion is the optical analog of X-rat temperature. Observationally: σ 2 = (1.0 ± 0.1) k B T lum / μ m p But this gas-mass weighted temperature, T lum, is typically ~20% higher than X-ray spectroscopic temperature (non-gravitational e fg ects? clumping?) 22 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Measuring velocity dispersion The velocity field traces the filamentary substructure Persistence of substructures (simulations by White, Cohn & Smit 2010) 23 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Radio observation of clusters 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. 327 MHz map of the mini-halo in the Perseus cluster (z = 0.018). 24 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Clusters detected by APEX-SZ 25 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
APEX telescope • 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 μ m 26 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
APEX-SZ instrument ● 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 27 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Joint SZ/X-ray modeling 28 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Density and temperature profiles 29 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Mergers, shocks and bubbles Perseus cluster Abell 2052 J0717.5+3745 at z = 0.548 Clearly disturbed, shock-like substructure, filament. What will SZ image look like? 30 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Future: SZ imaging with ALMA 31 Observational Cosmology Lecture 8 (K. Basu): Cosmology with Galaxy Clusters
Recommend
More recommend
