AAS 205th Meeting, 9-13 January 2005
Session 131 The Deep Dark Universe
Oral, Wednesday, January 12, 2005, 2:00-3:30pm, Royal Palm 4-6

## [131.07] Joint Efficient Dark-energy Investigation (JEDI): a Candidate Implementation of the NASA-DOE Joint Dark Energy Mission (JDEM)

Y. Wang (U. of Oklahoma), A. Crotts (Columbia), P. Garnavich (Notre Dame), W. Priedhorsky, S. Habib, K. Heitmann (LANL), A. Kutyrev, H. Moseley (NASA GSFC), G. Squires (Caltech), M. Tegmark (MIT), N. Wright (UCLA), JEDI Team

Dark energy, a mysterious energy component of the universe with negative pressure, has caused the observed acceleration of the expansion rate of the universe. Solving the mystery of the nature of dark energy is the most important problem in cosmology today. We propose a new mission concept, JEDI (Joint Efficient Dark-energy Investigation), for the NASA-DOE Joint Dark Energy Mission (JDEM). JEDI will provide three independent ways to probe dark energy: distance-redshift relations of type Ia supernovae (SNe Ia), baryonic oscillations from a galaxy redshift survey, and weak lensing cross-correlation cosmography. JEDI is the natural extrapolation to a space platform of the concept of an ultra-deep supernova survey proposed by Wang (1998).

JEDI will accomplish three primary scientific goals: (1) Measuring dark energy density as a free function of cosmic time to 10% accuracy or better from the data of over 20,000 SNe Ia with 0 \leq z \leq 1.7; (2) Obtain independent dark energy constraints from a redshift survey of 12 million galaxies to a redshift of 3-4 over 36 square degrees; (3) Obtain independent dark energy constraints from a weak lensing survey (complementary to the galaxy redshift survey) over 36 square degrees.

JEDI is a 2m aperture space telescope capable of simultaneous wide-field imaging and multiple object spectroscopy with a field of view of 1 square degree. Supernova spectroscopy is the bottle-neck'' for obtaining a large number of SN Ia events usable for cosmology; slits are needed to obtain sufficient signal-to-noise for SN Ia spectra. JEDI has the unique ability of simultaneously obtaining slit spectra for all objects in the wide field of view. The JEDI focal plane is centered by an imaging array consisting of five strips of NIR imaging detectors, covering the wavelength range of 0.8-4 \mum. On either side of the imaging array are 8 spectrograph fields, each consists of a 175x384 array of microshutters (each with a slit size 2"x5") --- four times as many as will be used by JWST. The wavelength coverage of the spectrograph fields is 0.8-2.5 \mum. JEDI uses a total of 200-300 HAWAII-2 2048x2048 HgCdTe detectors from Rockwell. JEDI will orbit in L2, with sunshields similar to those used by SIRTF. JEDI will conduct an ultra-deep survey of 36 square degrees over three years, yielding data simultaneously for the SN Ia, galaxy redshift, and weak lensing surveys. Because of JEDI's extraordinary efficiency of making SN Ia observations (especially at the high z end), we have the option of devoting the third year exclusively to a wide survey for galaxy redshifts and weak lensing measurements.

This work was supported in part by NSF CAREER grant AST-0094335.