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

Arlin Crotts, P. Garnavich+16 more|arXiv (Cornell University)|Jul 1, 2005

Astronomy and Astrophysical Research6 citations

TL;DR

JEDI proposes a 2m-class space telescope mission to probe dark energy using three independent methods: Type Ia supernovae as standard candles, baryon acoustic oscillations as a standard ruler, and weak gravitational lensing. It achieves 2% accuracy in measuring the cosmic expansion history H(z) across redshift bins of 0.2–0.3, enabling precise constraints on dark energy parameters with minimal systematic error through cross-method consistency.

ABSTRACT

JEDI will probe dark energy in three independent ways by measuring the expansion history of the universe: (1) using type Ia supernovae as cosmological standard candles over a range of distances, (2) using baryon oscillations as a cosmological standard ruler over a range of cosmic epochs, (3) mapping the weak gravitational lensing distortion by foreground galaxies of the images of background galaxies at different distances. JEDI will unravel the nature of dark energy with accuracy and precision. JEDI is a 2m-class space telescope with the unique ability of simultaneous wide-field imaging (0.8-4.2 micron in five bands) and multi-slit spectroscopy (0.8-3.2 micron) with a field of view of 1 square degree. What makes JEDI efficient is its ability to simultaneously obtain high signal-to-noise ratio, moderate resolution slit spectra for all supernovae and ~ 5000 galaxies in its wide field of view, and to combine imaging and spectroscopy so that the appropriate balance of time is devoted to each. JEDI will measure the cosmic expansion history H(z) as a free function to < 2% accuracy in redshift bins of 0.2-0.3. Assuming a flat universe and σ(Ω_m)=0.01 (0.03), JEDI could measure a departure from a vanilla ΛCDM model (w_0=-1, w'=0) with σ(w_0)=0.013 (0.031) and σ(w')=0.046 (0.063). JEDI will obtain the well-sampled lightcurves in Z, J, H, K, L bands and spectra of ~ 14,000 type Ia supernovae with redshifts ranging from 0 to 1.7; the redshifts of ~ 10-100 million galaxies to H ~ 23 and z ~ 4 over 1000-10,000 square degrees; and measurements of the shapes of galaxies over 1000-10,000 square degrees in Z,J,H,K,L for > 10^9 galaxies to H \~ 25.

Motivation & Objective

• To determine the nature of dark energy, the dominant component of the universe's energy budget.
• To measure the cosmic expansion history H(z) with 2% accuracy in redshift bins of 0.2–0.3 to rule out 90% of dark energy model parameter space.
• To minimize systematic errors by employing three independent, cross-checking methods: supernovae, baryon oscillations, and weak lensing.
• To achieve high-precision constraints on dark energy parameters w₀ and w′, with σ(w₀) = 0.013 and σ(w′) = 0.046 under a flat ΛCDM model.
• To deliver a robust, efficient mission design capable of handling large datasets across wide fields with simultaneous imaging and spectroscopy.

Proposed method

• JEDI employs a 2m-class space telescope with a 1 square degree field of view for simultaneous wide-field imaging (0.8–4.2 μm in five bands) and multi-slit spectroscopy (0.8–3.2 μm).
• It uses 64 HgCdTe detectors (2048×2048) and 8 microshutter arrays (175×384) to enable high signal-to-noise, moderate-resolution spectroscopy of all objects in the field, including supernovae and galaxies.
• The mission measures H(z) as a free function by combining data from three independent cosmological probes: Type Ia supernovae, baryon acoustic oscillations, and weak gravitational lensing.
• The telescope operates in a cold L2 orbit with passive cooling via sunshields, extending sensitivity beyond 4 μm to reduce dust extinction systematics.
• It obtains well-sampled light curves and spectra for ~14,000 Type Ia supernovae (z = 0 to 1.7), redshifts for 10–100 million galaxies (z ~ 4, H ~ 23), and galaxy shapes for >10⁹ galaxies (H ~ 25).
• Data from JEDI will be combined with Planck CMB data to further tighten constraints on dark energy models.

Experimental results

Research questions

• RQ1 What is the true nature of dark energy driving the universe’s accelerated expansion?
• RQ2 Can the cosmic expansion history H(z) be measured with 2% accuracy in redshift bins of 0.2–0.3 to constrain dark energy models independently of assumptions?
• RQ3 How can systematic errors in individual dark energy probes be minimized through cross-validation using three independent methods?
• RQ4 To what extent can JEDI’s multi-probe approach resolve discrepancies between supernova, baryon oscillation, and weak lensing measurements?
• RQ5 What are the achievable statistical uncertainties on dark energy parameters w₀ and w′ under a flat ΛCDM model?

Key findings

• JEDI can measure the cosmic expansion history H(z) with 2% accuracy or better in redshift bins of 0.2–0.3, enabling the exclusion of 90% of dark energy model parameter space.
• Under a flat universe, JEDI achieves σ(w₀) = 0.013 and σ(w′) = 0.046, improving to σ(w₀) = 0.031 and σ(w′) = 0.063 with conservative error estimates.
• The mission will obtain high signal-to-noise, well-sampled light curves and spectra for approximately 14,000 Type Ia supernovae across redshifts 0 to 1.7.
• JEDI will obtain redshifts for 10–100 million galaxies up to z ~ 4 and H ~ 23 over 1,000–10,000 square degrees.
• The weak lensing survey will cover 1,000–10,000 square degrees to H ~ 25, providing a 10% or better measurement of H(z) and serving as a critical cross-check.
• The mission’s design enables simultaneous imaging and spectroscopy across a wide field, maximizing efficiency and minimizing systematics through multi-method consistency.