Simulating the SZ Sky Predictions for Upcoming Sunyaev-Zel’dovich Effect Galaxy Cluster Surveys Eric J. Hallman CASA, University of Colorado 16 February, 2007 Clusters of Galaxies as Cosmological Probes Conference Aspen, CO
Jan 29, 2016
Simulating the SZ Sky
Predictions for Upcoming Sunyaev-Zel’dovich Effect
Galaxy Cluster Surveys
Eric J. Hallman
CASA, University of Colorado
16 February, 2007
Clusters of Galaxies as Cosmological Probes Conference
Aspen, CO
Collaborators
• Brian O’Shea (LANL)
• Jack Burns (University of Colorado)
• Mike Norman (UCSD)
• Rick Wagner (UCSD)
• Robert Harkness (SDSC)
SZ Surveys of Galaxy Clusters
• Survey yield depends on cosmology AND gas physics AND details of dynamical states of clusters
• How does observable scale with mass?
• What is the selection function in mass for cluster surveys?
• Also depends on instrument properties, survey strategy, confusion, etc.
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•ΛCDM m=0.3, =0.7, 8=0.9•AMR gives high resolution (8 h-1 kpc) in dense regions• 512 h-1 Mpc on a side, use 7 levels of refinement• 5123 root grid, 7 levels everywhere•DM mass = 7.3x1010 Msolar, baryon mass = 1.1x1010
•Initial run is adiabatic physics only
Adaptive Mesh Refinement (AMR) Light Cone Simulations (N-body + Hydro)
Enzo (O’Shea et al. 2005, http://cosmos.ucsd.edu/enzo)
How do we make simulated surveys?
• Surveys sample the universe at all observable epochs, so….
• Stack simulations at different evolutionary states in discrete redshift intervals to approximate
• Each z uses physical extent of box in line of sight which matches that redshift interval
• Modify angular scale of image to fixed angular size for all redshifts, flux diminishes (but not in SZE!)
• Random shifting, rotating, some tiling• Model telescope response, background, foreground
contamination, point sources, etc etc (Future work)
Sky Surveys
• X-ray and SZE synthetic surveys• 5000+ Clusters above 1x1014Msolar in field out to z=3• 2048x2048, 10x10 degrees, 17.6” / pixel
Why do we have N-body + hydro?
• In real universe, clusters are neither isothermal nor in equilibrium generally (e.g. M. Voit’s talk)
• Variations in cluster physics make a difference (Evrard’s and Rudd’s talks)
• In order to characterize scatter, survey selection (in mass) from simulations, must include baryons!
Cold Fronts Filaments Bullet Subcluster
1E 0657-56Abell 1795Abell 2256
(Sun et al 2002) (Fabian et al 2001) (Markevitch et al 2002)
Clusters are NOT generally in equilibrium (dynamical, hydrostatic or otherwise)
Merger Boosting
• See also C. Sarazin’s talk
Identification of Sources
• Hallman et al. 2007
Identification with SExtractor
• Upcoming Surveys:
SPT: 1.0’, ~4000deg^2, 10K
APEX-SZ: 1.0’, ?deg^2, 10K
ACT: 1.7’,100-200deg^2,2K
Planck, 5.0’, all-sky, 2.2K
• 90% limits for 200 stacking realizations of the survey
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• APEX: 472 +- 100
• ACT: 1211+- 200
• Planck: 90 +- 40
What else should be included?
• What we get: full array of dynamical stateslarge volumegaussian background
• What we’re missing (so far) ref. N. Sehgalatmospherepoint sourcesadditional physicsother instrumental effects We are working on all of these!
Halos in the Simulation
• Identify via HOP algorithm
• 12000 clusters at z=0 in simulation box above M = 5x1013Msolar
• Identify their locations in the 2d projection of the simulated survey
• Match to locations of halos provided by SExtractor
• Hallman et al. 2007
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Recall L. Verde’s talk
Stacking Caveats
• Stacking with a single simulation has problems
• Constant physical resolution (as f(z)) on the grid does not equal constant angular resolution on the sky
• Large scale correlations can be generated
• How can we solve that? Use multiple simulations!
The Big One(s)
• We are generating a complete, unique numerical simulation for each z
• Each simulation has a physical size specified by it’s angular extent at that redshift (ITC 10 degrees square).
• Allows lower computational effort for the most nearby volumes, since their physical resolution must be highest.
• Eliminates stacking issues (almost).• 2 cubic Gpc of total simulated volume
Plans for Huge LCs
• From smaller set of simulations, refine baryonic physics (cooling, star formation, SN feedback, AGN feedback, conduction, etc.)
• Vary cosmology (e.g., w, 8), determine precision necessary to distinguish
• Synthetic Observations (X-ray/SZE primarily) including both instrumental effects, backgrounds/foregrounds, etc.
Summary
• Survey yields depend on luminosity function, which depends on cosmology AND detailed baryonic physics AND dynamical states AND confusion, etc.
• If you want high precision, non-trivial problems in counting clusters
• Numerical N-body + hydro (!) simulations coupled with realistic synthetic observations allow us to understand systematics, get the “right” answer!
Sample Stacking Solution
Synthetic Observations
Constraints from Clusters, Dark Energy Equation of State
• Haiman et al 2001
Results from Adiabatic Physics Model (Projected Emission-Weighted Temperature)
5 Mpc