DES Cluster Simulations and the ClusterSTEP Project M.S.S. Gill (OSU / CBPF / SLAC) In collaboration with: J. Young, T.Eifler, M.Jarvis, P.Melchior and other DES members Pixels to Shears Workshop, University of Edinburgh Friday, Jan 28, 2011

Our first ‘end-to-end’ DES simulations results from full analysis of a SIS simulated cluster Progressing next to: ClusterSTEP More complex ray-traced simulation Higher statistics Includes: PSF variation, seeing levels Will be publically released 2

II. The Dark Energy Survey (DES) Cluster Simulations 3 DES: Probe the nature of dark energy with Supernovae Baryon oscillations Clusters of galaxies Weak gravitational lensing

Our Initial DES Cluster Simulation All 62 chips are simulated (H. Lin and N. Kouropatkin) Stepped up in increasing complexity: Start with just background galaxies Add in shear Add in noise Add in psf Add in stars Add in cluster and foreground galaxies Publically available to all at: ccapp.osu.edu/DEScluster (See Gill et al. 2009, arXiv: )arXiv:

CLUSTER IMAGE INFORMATION  Truth Table Information contains: ­ (RA, DEC) and (x,y) pixel positions for each object ­ Redshift of galaxy objects ­ grizy Magnitudes ­ Theoretical shear for galaxy object positions  Image (only in one band): ­ Corresponds to truth r Magnitude ­ Theoretical shear convolved with intrinsic object ellipticity  Shear applied only for gamma < 0.2 ( beyond ~400 pixels = 80” = 72 kpc for z=0.3), to avoid strong lensing regime.  Full plane radius: ~15k pixels (pixelscale=0.27”/pixel) [ Cluster simulation made by H. Lin and N. Kourapatkine at FNAL]

APPLIED CLUSTER SHEAR DES Full plane: averages of truth shears in cells inside of each CCD. Each CCD is split into equally sized 8x4 cells. Same thing but close up on cluster center pixels Input: sigma_v = 1250 km/sec

SIMULATED IMAGES Low Noise No Noise High Noise Stars + Bkgd Gals All images here show same part of CCD 28 – containing cluster center Stars + Bkgd Gals Stars + Bkgd AND Frgnd Gals Stars + Bkgd AND Frgnd Gals

SIS Fits to the DES simulation Screen clipping taken: 2/17/2009, 2:43 AM After PSF correction, shear matches truth within error Fit to SExtractor ellip = pink solid Truth fit = red solid Fit to extracted ellip. = dashed Shear vs. radial distance from center in pixels Each cyan or red point represents one galaxy with its ‘observed’ ellipticity – an unbinned fit is then done to these points

Results: E-mode PROFILES Using r-i>0.6 Color Cut Files z = 0.8z = exact Z = EXACTSHAPELETS Z = EXACTIMCAT Z = EXACTTRUTH Z = 0.8SHAPELETS [ RJM et al. ] Z = 0.8IMCAT Z = 0.8TRUTH UncertaintyσvREDSHIFT CORRECTIONFILE # sigma away Many Fit Output Low Noise File, bkgd gals picked by color

10 Moving to ClusterSTEP - Goals To extend results of STEP to high shear regime as would be found near clusters (g~ vs. g<~ 0.05 in STEP) -- const shear images also being made To compare performance of modern pipelines on cluster images and see how errors in shape measurement propagate to final mass estimate To performing tests under different variations: e.g. noise level, PSF model, galaxy selection in simulated images (cf. van Waerbeke 2001ish)

11 Making ClusterSTEP Images Start from R. Wechsler et al.’s full-scale N-body cosmological simulations for DES Ray-trace so that shear naturally follows properly from realistic cluster profiles Resulting shear is then applied back to galaxies in images

12 Example of shear results from full DECam plane Colored symbols are clusters (color  redshift, size  mass) Shear map is from truth info here This is old, get halo 2 or 6, we’ll pick just One per image, only selected ones are Good according to Matt

13 Typical realistic DECam focal plane PSF New ones will have higher corner PSF, with ellipticity up to 0.05, may be more complex also (atm turbulence would do this) Here: Longest whiskers are e ~ 0.01

14 Variation of results with PSF variation IMCAT Vs. Truth Fits shown

Conclusions and Next Steps Able to robustly reconstruct input velocity dispersion in initial simulation Now moving to more realistic ClusterSTEP images with ray-tracing Will get more robust answers for variation of cluster mass with differing observational conditions/cuts Eventually plan to open this to public participation 16

Thx for organizing a “GREAT” workshop! :-> 16 Click to edit Master text styles Second level Third level Fourth level Fifth level In Bonny Ole Scotland !

17 Extra Slides

SIMULATION FILES SUITE AcronymFile DescriptionNoiseShearContents OFOriginal NonshearedNone Background Galaxies SFShearedNoneCluster ShearBackground Galaxies NFNoise-addedHighCluster ShearBackground Galaxies HPFHN PSF-addedHighCluster Shear + PSF Background Galaxies Stars HFFHN Foreground Galaxies Added -- like a 600 sec DES exposure HighCluster Shear + PSF Background Galaxies Stars Foreground Galaxies LPFLN PSF-addedLowCluster Shear + PSF Background Galaxies Stars LFFLN Foreground Galaxies Added LowCluster Shear + PSF Background Galaxies Stars Foreground Galaxies Most realistic images are in red; Noise: LN ~ 1/13 * HN

Full Field Simulation Model psf From stars (Imcat)

20 Individual galaxies inside the clusters Degrees (RA) Degrees (Dec)