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Supernova / Acceleration Probe: A Satellite Experiment to Study the Nature of the Dark Energy

SNAP Collaboration, G. Aldering, W. Althouse, R. Amanullah, J. Annis, P. Astier, C. Baltay, E. Barrelet, S. Basa, C. Bebek, L. Bergstrom, G. Bernstein, M. Bester, B. Bigelow, R. Blandford, R. Bohlin, A. Bonissent, C. Bower, M. Brown, M. Campbell, W. Carithers, E. Commins, W. Craig, C. Day, F. DeJongh, S. Deustua, T. Diehl, S. Dodelson, A. Ealet, R. Ellis, W. Emmet, D. Fouchez, J. Frieman, A. Fruchter, D. Gerdes, L. Gladney, G. Goldhaber, A. Goobar, D. Groom, H. Heetderks, M. Hoff, S. Holland, M. Huffer, L. Hui, D. Huterer, B. Jain, P. Jelinsky, A. Karcher, S. Kent, S. Kahn, A. Kim, W. Kolbe, B. Krieger, G. Kushner, N. Kuznetsova, R. Lafever, J. Lamoureux, M. Lampton, O. Le Fevre, M. Levi, P. Limon, H. Lin, E. Linder, S. Loken, W. Lorenzon, R. Malina, J. Marriner, P. Marshall, R. Massey, A. Mazure, T. McKay, S. McKee, R. Miquel, N. Morgan, E. Mortsell, N. Mostek, S. Mufson, J. Musser, P. Nugent, H. Oluseyi, R. Pain, N. Palaio, D. Pankow, J. Peoples, S. Perlmutter, E. Prieto, D. Rabinowitz, A. Refregier, J. Rhodes, N. Roe, D. Rusin, V. Scarpine, M. Schubnell, M. Sholl, G. Smadja, R. M. Smith, G. Smoot, J. Snyder, A. Spadafora, A. Stebbins, C. Stoughton, A. Szymkowiak, G. Tarle, K. Taylor, A. Tilquin, A. Tomasch, D. Tucker, D. Vincent, H. von der Lippe, J-P. Walder, G. Wang, W. Wester

Abstract

The Supernova / Acceleration Probe (SNAP) is a proposed space-based experiment designed to study the dark energy and alternative explanations of the acceleration of the Universe's expansion by performing a series of complementary systematics-controlled measurements. We describe a self-consistent reference mission design for building a Type Ia supernova Hubble diagram and for performing a wide-area weak gravitational lensing study. A 2-m wide-field telescope feeds a focal plane consisting of a 0.7 square-degree imager tiled with equal areas of optical CCDs and near infrared sensors, and a high-efficiency low-resolution integral field spectrograph. The SNAP mission will obtain high-signal-to-noise calibrated light-curves and spectra for several thousand supernovae at redshifts between z=0.1 and 1.7. A wide-field survey covering one thousand square degrees resolves ~100 galaxies per square arcminute. If we assume we live in a cosmological-constant-dominated Universe, the matter density, dark energy density, and flatness of space can all be measured with SNAP supernova and weak-lensing measurements to a systematics-limited accuracy of 1%. For a flat universe, the density-to-pressure ratio of dark energy can be similarly measured to 5% for the present value w0 and ~0.1 for the time variation w'. The large survey area, depth, spatial resolution, time-sampling, and nine-band optical to NIR photometry will support additional independent and/or complementary dark-energy measurement approaches as well as a broad range of auxiliary science programs. (Abridged)

Supernova / Acceleration Probe: A Satellite Experiment to Study the Nature of the Dark Energy

Abstract

The Supernova / Acceleration Probe (SNAP) is a proposed space-based experiment designed to study the dark energy and alternative explanations of the acceleration of the Universe's expansion by performing a series of complementary systematics-controlled measurements. We describe a self-consistent reference mission design for building a Type Ia supernova Hubble diagram and for performing a wide-area weak gravitational lensing study. A 2-m wide-field telescope feeds a focal plane consisting of a 0.7 square-degree imager tiled with equal areas of optical CCDs and near infrared sensors, and a high-efficiency low-resolution integral field spectrograph. The SNAP mission will obtain high-signal-to-noise calibrated light-curves and spectra for several thousand supernovae at redshifts between z=0.1 and 1.7. A wide-field survey covering one thousand square degrees resolves ~100 galaxies per square arcminute. If we assume we live in a cosmological-constant-dominated Universe, the matter density, dark energy density, and flatness of space can all be measured with SNAP supernova and weak-lensing measurements to a systematics-limited accuracy of 1%. For a flat universe, the density-to-pressure ratio of dark energy can be similarly measured to 5% for the present value w0 and ~0.1 for the time variation w'. The large survey area, depth, spatial resolution, time-sampling, and nine-band optical to NIR photometry will support additional independent and/or complementary dark-energy measurement approaches as well as a broad range of auxiliary science programs. (Abridged)

Paper Structure

This paper contains 41 sections, 18 figures.

Table of Contents

  1. Introduction
  2. Cosmology with Supernovae
  3. Control of Systematic Uncertainties
  4. Known Sources of Systematic Uncertainties
  5. Possible Sources of Systematic Uncertainties
  6. Systematic-Error Model
  7. Comparing Defined Subsets of Supernovae
  8. Supernova Sample to Probe Dark Energy
  9. Cosmology with Weak Lensing
  10. Weak Lensing as a Probe of Dark Energy
  11. Advantages of Space-Based Measurements
  12. Joint SNAP Constraints on Dark Energy from Weak-lensing, Supernova, and other Measurements
  13. Reference Model SNAP Experiment
  14. Reference Model Observation Strategy and Data Package
  15. Supernova Program
  16. ...and 26 more sections

Figures (18)

  • Figure 1: There is strong evidence for the existence of a cosmological vacuum energy density. Plotted are $\Omega_M$---$\Omega_\Lambda$ 68% and 95% confidence regions for supernovae knopetal:2003, cluster measurements (based on allenetal:2003), and CMB data with $H_0$ priors (outer counters from Lange:2001, inner contours from spergel:2003). These results rule out a simple flat $\Omega_M=1$, $\Omega_\Lambda=0$ cosmology. Their consistent overlap is a strong indicator for dark energy. Also shown is the expected confidence region from just the SNAP supernova program for $\Omega_M=0.28, \Omega_\Lambda=0.72$.
  • Figure 2: Best-fit 68%, 90%, 95%, and 99% confidence regions in the $\Omega_{\rm M}$--$w$ plane for an additional energy density component, $\Omega_w$, characterized by an equation-of-state $w = p/\rho$ using supernovae alone knopetal:2003. The fit is constrained to a flat cosmology ($\Omega_{\rm M} + \Omega_w =1$). Also shown are the expected 68% and 95% confidence regions allowed by just the SNAP supernova program assuming the fiducial values $w=-1$ and $\Omega_M=0.28$.
  • Figure 3: Sample B-band light curve for a $z=0.8$ Type Ia supernova. Signal-to-noise targets are shown at different epochs for identification of possible systematic effects.
  • Figure 4: Type Ia spectra at maximum light showing line features associated with possible Type Ia supernova variation. The horizontal axis shows observer frame wavelengths for $z=0$ and $z=1.7$ supernovae.
  • Figure 5: From hut:2003, accuracy in estimating the equation of state variation parameter, $w'$, as a function of maximum redshift probed in supernova distance surveys. The lower two curves assume priors in $\Omega_M$ good to 0.01, while the upper two curves are for the case where systematic uncertainties are present. The top, heavy curve corresponds to the most realistic case. It is clear that even with modest systematic uncertainties good accuracy requires probing to high redshift. In all cases a flat universe is assumed.
  • ...and 13 more figures