The DoE/NASA Joint Dark Energy Mission. November 2005 Kim Griest

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1 The DoE/NASA Joint Dark Energy Mission November 2005 Kim Griest

2 JDEM Science Definition Team (SDT): Cochairs: Chuck Bennett and Kim Griest Members: Albrecht, Baltay, Barish, Bernstein, Blandford, Caldwell, Cheng, Deustra, Donahue, Eisenstein, Ellis, Freedman, Frieman, Gardener, Glazebrook, Kirshner, Lauer, Levi, Linder, Lupton, Moos, Morse, Perlmutter, Rausher, Riess, Seiffert, Wheeler, Wright Charge: advice to DoE/NASA on what JDEM should do; AO will be written based upon our report

3 Discover and characterize the nature of the dark energy with a space mission JDEM idea extremely highly rated by NAS, DoE, NASA, etc: great support everywhere Very little current money and current total cost cap is $600M, but may cost more Date of launch, even of AO not clear (money) Started out as SNAP (Super Nova Acceleration Probe) led by DoE s LBL, but when NASA joined required a competition

4 NASA: Beyond Einstein Probes few hundred thousand dollars, but now several million from NASA for JDEM Mission Concept Design (SNAP, DESTINY, JEDI, ADEPT) DoE spent substantial amount on LBL, etc. effort (all on SNAP)

5 What Science will JDEM do? Depends upon what method is chosen! Top contenders are SNIa and weak lensing => wide field imager and spectrograph Baryon oscillations and X-ray clusters also being studied and might compete Key: able to do substantially better than from the ground

6 How to compare different experiments? Need to know what we are looking for; i.e. what is DE and how to characterize it! Help from theorists? No compelling models Comparison depends on goal: Cosmo-illogical constant or not? But is w= good enough? ? ? Again theoretical guidance is lacking Is w changing in time? Constraint in w, w plane? w vs. w_a? To what accuracy is w needed? Consider big change at early redshift? Is GR correct?

7 My opinion: eventually need both geometry (SN or BAO) and growth of structure (WL or?) methods to test GR, but will both be needed from space? Will it be too expensive to do all from space? With no specific absolute target goal, can only compare and rank different experiments and methods But different methods/experiments are sensitive to different redshift range => different types of DE To compare power of experiments, JDEM SDT is creating set of fiducial models with behaviors that hopefully span the range of reasonable possibilities

8 We specify priors (e.g. value and error in H0; value of Omega_tot) and model parameters and ask each proposer to calculate how well their experiment measures the appropriate parameters (e.g. w, w_a) Besides Lambda, and simple quintessence, will have models with DE contribution at higher redshift and models which do not follow GR Wide Field camera in space has many purposes: Should JDEM do ancillary science? Community support better, but DoE vs. NASA Cost for longer mission is substantial (Guest observers) Is JDEM a wide field camera at all?

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10 Most developed JDEM mission concept is SNAP 2 meter aperature wide field imager in L2 orbit 1/3 square degree for SNIa and weak lensing 6 optical ( nm, 0.1 arcsec/pixel) and 3 IR ( nm, 0.17 arcsec/pixel) filter bands: (total around 600 M pixel) Spectrograph (R=100) for SN spectra Very stable PSF, good control of systematics

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12 SNAP Surveys Deep 15 sq deg survey every 4 days for SNIa search: in 2 years get 2000 SNIa with excellent spectra and lightcurves out to z=1.7 Wide weak lensing survey: perhaps 1000 square degrees to AB 27.7, or sq deg to 26.7? Goal is w to 4% and w to 10% (is this good enough?)

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16 2 meter mirror, HgCdTe arrays, L2 orbit, SNIa and SNII out to z=1.7 Measure w to 0.05, w to 0.2

17 JEDI Yang, Crotts, Garnevich, Priedhosky, Habib, Heitmann, Kutyrev, Moseley, Squires, Tegmark, Wright 2 meter, wide field (1 sq deg) plus slit spectroscopy (1 by 5 micro-shutters) for all objects in field NIR.8-4 micron, ~250 2Kx2K HgCdTe 3 years: SNIa over 36 deg sq to z=1.7, redshift survey to z=~4, weak lensing L2 orbit, dark energy density vs time to 10% or better

18 ADEPT C.Bennett, etc. Still being designed: 1 meter mirror, baryon acoustic oscillations? Etc.???

19 Conclusions Dark Energy problem is important enough and has enough support that a space mission will be flown as long as substantial improvement over ground is convincingly proved. Time scale is uncertain, cost cap uncertain, method uncertain, but probably will include SNIa and/or weak lensing.

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