1. Surveying the Universe with SNAP Tim McKay University of Michigan Department of Physics Seattle AAS Meeting: 1/03 For the SNAP collaboration

2. The Supernova/Acceleration Probe Mostly pure survey mode Step and stare across the sky, each location seen in all nine filters Dithered exposures at each location Two surveys: a deep, time domain SNe survey and wide single pass weak lensing survey A space based optical/near-IR survey telescope Large field of view coupled with 0.1” resolution and broad coverage

3. SNAP Deep & Time Domain Survey Base SNAP survey: 15 square degrees near ecliptic poles ~6000x as large as ACS deep field, to m AB =30.4 in nine optical and IR bands Provides ≥ 100 epochs over 16 months (each to m AB =27.8) for time domain studies in all nine bands GOODS Survey area Hubble Deep Field

4. SNAP Wide Weak Lensing Survey ~300 square degree ‘wide’ survey surrounding each of the deep fields Roughly five months of observing time Four dithered 500 second exposures at each location; sensitive to m AB =28.1 Every field observed in all nine optical NIR filters GOODS Survey area Hubble Deep Field

5. SNAP imaging surveys are unique Depth —From the disk to z=10 —Depth in the time domain; R~27.8 in each epoch Optical + NIR —9 bands = Low resolution spectroscopy (R~7) —Available in time domain —NIR follows Lyman-  emission to z=12 Image quality —High resolution —PSF stability Photometric stability Some of the topics impacted: 1.Galaxy studies: evolution and clustering, a census of R, I, z, and J band dropout galaxies 2.Galaxy clusters: identification of high redshift galaxy clusters, faint and small constituents 3.High-z quasar studies: mapping the quasar luminosity function to z=10, probing the structure of reionization 4.Transients; GRBs, QSO/AGN, outer solar system objects 5.Cool stars in the Milky Way 6.Lensing: evolution of the galaxy-mass correlation to z=1, cluster masses, etc. 7.Targets: Identification of targets for JWST, CELT, etc…

6. Galaxy evolution and photo-z HDF’s illustrate the potential impact of SNAP studies Large area observations required to probe environmental effects at each redshift High resolution for structure and population studies Photo-z: —4000Å break for z=0-3.0 —Ly-  break for z=3.3-12 —NIR for dust and high z ≥5x10 7 galaxies with photoz Family of Galaxy Spectra: Budavari et al.

7. Simulated SNAP Photo-z Expected photo-z performance for SNAP multiband survey is excellent (  z~0.04/galaxy) Spatially resolved color gives photo-z + stellar population information Conti & Connolly: Jan. 2002 AAS Spectroscopic z Photometric z Single band imageSFR per pixel

8. Linear survey size (h -1 Mpc) J. Colberg, VIRGO simulations: Jenkins et al, 1998 ApJ,499,20-40 Evolution of Galaxy Clustering Photo-z defines redshift sheets Evolution of 2D clustering 12 nearly independent redshift sheets from z=0-3 Optical/NIR covers restframe optical out to z=3, simplifying evolution studies Wide fields substantially reduce sensitivity to cosmic variance constraints Conti and Connolly Jan 2002 AAS Relative Error 10%

9. Finding clusters in SNAP data Important markers of structure formation which form relatively late. dn/dz exquisitely sensitive to cosmology; alternate dark energy probe? Widefield multicolor CCD data has revitalized optical cluster finding —Cluster members are the reddest galaxies at each redshift —Clusters in position-color space Z=0.165 SDSS image of Abell 1553

10. Identification of high-z clusters Clustering in position- color space essentially eliminates contamination by projection Gladders & Yee (2000), Goto et al. (2001), Annis et al. (2002) E/SO ridgeline provides extremely accurate (  z  0.01) photometric redshift Red sequence in place at z>1 Red sequence galaxies at z=1.27 (van Dokkum et al, 2000) i magnitude g-r color E/SO ridgeline

11. Z=0.041 Z=0.138 Z=0.277 Z=0.377 Example color cluster images from the SDSS

12. Expected SNAP cluster counts 15 square degree survey still suffers from cosmic variance. 300 square degree lensing survey will be more useful for cluster counts Based on Virgo consortium Hubble Volume  CDM Simulations N (M>5x10 13 M  ) in 15 sq. deg. Redshift in bins of 0.02 z=1 z=2 z=3

13. Quasar evolution to z>12 Quasar identification through multicolor observations Further selection through variability Good QSO redshift estimates through photoz Depth extends to 1000x less luminous objects NIR extends to much higher redshift (from 6.3-12) SDSS QSO color selection Fan et al., AJ, 2000

14. Setting up reionization probes Highest redshift SDSS QSO’s show evidence for Gunn-Peterson absorption associated with neutral IGM Possibly seeing edge of reionization epoch Structure in reionization is unknown: caused by variations in UV flux from early stars + quasars SNAP discovered z>6 QSO’s, with NGST spectroscopy, can map the spatial structure of reionization Pentericci et al, 2001 z=6.3 quasar Fan et al., 2002 Gunn-Peterson Optical Depth Redshift Wavelength f (erg cm- 2 s -1 A -1 )

15. Quasar number counts X. Fan, based on SDSS QSO LF Z > 5 Z > 7.5 Z > 10 One in SNAP deep survey AB magnitude Quasars per square degree

16. SNAP high-z weak lensing studies Beyond cosmology: galaxy and cluster studies To measure lenses at z=1.0 requires many sources at z~3.0 Ground based studies resolve galaxies to R~25, this limits available sources To study lenses at and beyond z=1 requires space based NIR observations —Evolution of galaxy- mass correlation function —Mass selected galaxy cluster number density and clustering —Mass maps of filaments

17. Why go so faint? Basic geometry is similar for the three surveys. Sensitivity changes due to available source density. Lensing S/N is much higher for a deeper space based survey. Sensitivity tilted to low-z. 25 28 30

18. SNAP Surveys and NG Telescopes Wide area surveys have always fed massive spectroscopic instruments —Palomar 48” > 200” —SDSS > 8-10m’s —SNAP > JWST, CELT and other next generation ground-based telescopes Biggest HST deep survey will be ACS survey: —6300x smaller than SNAP main survey —About as deep SNAP NIR survey capabilities especially important