# Presentation: 080708

## Shedding Light on Dark Energy with the SuperNova/Acceleration Probe (SNAP) Gregory TarléPhysics DepartmentUniversity of Michigan

**Shedding Light on Dark Energy with the ****S****uper****N****ova/****A****cceleration ****P****robe (****SNAP****)** Gregory TarléPhysics DepartmentUniversity of Michigan

- 2005 Aspen Winter ConferenceThe Highest Energies February 17, 2005

## Welcome to Applied String Theory 501!  (Winter 2055)

- We will start this course by having you do a simple and straightforward “warm-up” exercise.
- Show that the energy contained in the 1 m3 _empty_ box pictured here is 6.3  10-10 J.

- 1 m

- 1 m

- 1 m

## Golden Age of Cosmology

- New
- Standard Cosmology:
- 73±4% Dark Energy
- 27±4% Matter
- 0.5% Bright Stars
- Matter (27%):
- 22% CDM, 4.4% Baryons, 0.3% s

-  Weak lensing mass census
-  Large scale structure measurements
- M= 0.3

## A Fish Out of Water

- Q: What dominates this picture?
- A: The Water
- The discovery of Dark Energy has highlighted our feeble understanding of the nature of the vacuum.
- 20th century (Discovery of elementary particles, QM, SR, QFT, Renormalization... Standard Model)                          	  The century of the elementary particle.
- 21st century (Higgs, Inflation, Dark Energy, String Theory...)                                                                     The century of the vacuum.

- Photo by  L. Sander

## What we don’t know 

- Wouldn’t it be nice if in 10 years we could say, for example:
- The dark energy is a dynamical scalar field with an equation of state today of *w *(*z *= 0)  *w**0 *= -0.82 ± 0.05.  The time variation of the EOS is dw/dz* ** w ́ *= 0.29 ± 0.11 consistent with Supergravity inspired field theories..

- What we don’t know

- Precisely how much mass density (M) and dark energy density (DE) is there?  How flat is the universe?
- What is the equation of state     (w = p/) of the universe and how has it changed in time?

- 	What is the “dark energy?” Theorists have proposed a number of models, each with different properties w(z) that we can measure. Each brings a new understanding as to the nature of the vacuum.

- Lots of theories, little data!

##              Type Ia SNe: The Best Tool

-              Type Ia SNe: The Best Tool

**Can measure both intensity and spectra as the supernova brightens and fades over many days.**** **

- Comparison of SN Ia redshifts and magnitudes provides straightforward measurement of the changing rate of expansion of the universe:
-   Apparent magnitude measures distance (time back to explosion)
-   Redshift measures the total relative expansion of the universe since that time
-  Analysis of the spectra characterizes the details of the explosion and helps to control potential systematic errors.

** ****Type Ia supernovae (SNe Ia) provide a bright “standard candle” that can be used to construct a Hubble diagram looking back over both the acceleration and decelleration epochs of the universe.**
**  ****Accretion sends white dwarf mass near Chandrasekhar limit, leading to C,O detonation (********C ****~ 10****9 ****g/cm****3****) and complete thermonuclear deflagration of the star.**
** ****Each one is a strikingly similar explosion event with nearly the**** ****same peak intensity****.**

## The Expansion History of the Universe

**Need lots of **
**precision**
**data to study**
**this region**

## It’s a SNAP!

- A large wide-field space telescope with a 0.6 Gpixel visible/NIR imager and a visible/NIR spectrograph will provide:
-  a much larger statistical sample of supernovae (~2000 SNe with ~50 SNe/0.03 z).
-  much better controlled systematic errors (1 – 2%).
-  Precision photometery over a much larger range of redshifts (out to z = 1.7) than can be obtained on the ground.

## The SNAP Collaboration

| LBNL | G. Aldering, S. Bailey, C. Bebek, W. Carithers, T. Davis†, K. Dawson, C. Day, 
R. DiGennaro, S. Deustua†, D. Groom, M. Hoff, S. Holland, D. Huterer†, A. Karcher, 
A. Kim, W. Kolbe, W. Kramer, B. Krieger, G. Kushner, N. Kuznetsova, R. Lafever, 
J. Lamoureux, M. Levi, S. Loken, B. McGinnis, R. Miquel, P. Nugent, H. Oluseyi†, 
N. Palaio, S. Perlmutter, N. Roe, H. Shukla, A. Spadafora, H. Von Der Lippe, 
J-P. Walder, G. Wang |
| --- | --- |
| Berkeley | M. Bester, E. Commins, G. Goldhaber, H. Heetderks, P. Jelinsky, M. Lampton, 
E. Linder, D. Pankow, M. Sholl, G. Smoot, C. Vale, M. White |
| Caltech | R. Ellis, R. Massey†, A. Refregier†, J. Rhodes, R. Smith, K. Taylor, A. Weintein |
| Fermi National Laboratory | J. Annis, F. DeJongh, S. Dodelson, T. Diehl, J. Frieman, D. Holz†, L. Hui,  S. Kent, 
P. Limon, J. Marriner, H. Lin, J. Peoples, V. Scarpine, A. Stebbins, C. Stoughton, 
D. Tucker, W. Wester |
| Indiana U.

IN2P3-Paris
    -Marseille | C. Bower, N. Mostek, J. Musser, S. Mufson

P. Astier, E. Barrelet, R. Pain, G. Smadja†, D. Vincent
A. Bonissent, A. Ealet, D. Fouchez, A. Tilquin |
| JPL | D. Cole, M. Frerking, J. Rhodes, M. Seiffert |
| LAM (France) | S. Basa, R. Malina, A. Mazure, E. Prieto |
| University of  Michigan | B. Bigelow, M. Brown, M. Campbell, D. Gerdes, W. Lorenzon, T. McKay, S. McKee,
M. Schubnell, G. Tarlé, A. Tomasch |
| University of Pennsylvania | G. Bernstein, L. Gladney, B. Jain, D. Rusin |
| University of  Stockholm | R. Amanullah, L. Bergström, A. Goobar, E. Mörtsell |
| SLAC | W. Althouse, R. Blandford, W. Craig, S. Kahn, M. Huffer, P. Marshall |
| STScI | R. Bohlin, D. Figer, A. Fruchter |
| Yale U. | C. Baltay, W. Emmet, J. Snyder, A. Szymkowiak,  D. Rabinowitz, N. Morgan |
|  | †Institutional affiliation |

## Instrument Concept

- Baffled Sun Shade

- Solar Array, ‘Sun Side’

- 3-mirror anastigmat
- 2-meter Telescope

- Spacecraft Bus

- Solar Array, ‘Dark Side’

- Instrument Radiator

- Instrument Suite

## Instrument Concept

- Baffled Sun Shade

- Solar Array, ‘Sun Side’

- 3-mirror anastigmat
- 2-meter Telescope

- Spacecraft Bus

- Solar Array, ‘Dark Side’

- Instrument Radiator

- Instrument Suite

## Focal plane 

- Focal plane

## Supernova measurements

**Supernova measurements**

**Photometry**
**Discover a few thousand SNe from        z = 0.3 to 1.7.**
**Repetitive 4-day scans of a sky field (N or S ecliptic poles) over many months.**
**Automatic discovery and follow-up**
**Light curves in 9 filter bands from 0.35 ****μ****m to 1.7 ****μ****m to standardize the SNe.**

**Spectroscopy**
**Near peak brightness.**
**0.35 ****μ****m to 1.7 ****μ****m.**
****** ****~ 100 for max S/N.**
**Identify spectral features to select type Ia SNe, and group them according to parameters to reduce systematic errors.**
**Spectrum of host galaxy desirable.**

## Why go to high redshifts?

- probe the variability of w, providing an essential clue to the nature of DE.
- measure w0 precisely to determine whether it is a cosmological constant.

- Dark energy has been detected at low redshift (SCP, High-z). To determine what it is,and not just that it is, requires observations over both the acceleration and deceleration epochs.
- This long reach breaks essential degeneracies which low redshift data alone cannot.

- zmax=1.7

- zmax=0.7

## Rest frame B and V shift to NIR

- Simulated SNAP observations of high redshift SNe

- NIR
- Bands

- Rest frame V

- Rest frame B

- Z = 0.8

- Z = 1.2

- Z = 1.6

- Optical
- Bands

## This can’t be done on the ground!

- Optical
- Bands

- Simulated 8m telescope ground based observations of high redshift SNe

- Z = 0.8

- Z = 1.2

- Z = 1.6

- NIR
- Bands

## SNe IA population evolution
Shifting distribution of progenitor mass/metallicity/C-O
Shifting distribution of SN physics parameterss:
Amount of Nickel fused in explosion
Distribution of Nickel
Kinetic energy of explosion
Opacity of atmosphere's inner layers
Metallicity

Gravitational Lensing (de)amplification

- Shifting distribution of progenitor mass/metallicity/C-O
- Shifting distribution of SN physics parameterss:
- Amount of Nickel fused in explosion
- Distribution of Nickel
- Kinetic energy of explosion
- Opacity of atmosphere's inner layers
- Metallicity
- Gravitational Lensing (de)amplification

- Dust/Extinction
- Dust that reddens
- Evolving gray dust
- Clumpy
- Homogeneous
- Galactic extinction model
- Observational biases
- Malmquist bias differences
- non-SN Ia contamination
- K-correction uncertainty
- Color zero-point calibration

- Confronting Systematic Errors

- NIR fixes these

- Spectroscopy fixes these

## SNAP Deep & Time Domain Survey

- Basic SNAP SNe survey: 15 square degrees near ecliptic poles.
- ~ 6000x as large as ACS deep field, to mAB = 30.4 in nine optical and IR bands.
- Provides ≥ 100 epochs over 16 months (each to mAB = 27.8) for time domain studies in all nine bands.

- GOODS Survey area

- Hubble Deep Field

- The Moon

## Understanding Dark Energy

## Determination of CosmologicalParameters

*SNAP* will measure(if w= -1) to  0.02  andM to  0.03.
- With prior M measured by other techniques (e.g. CMB)to  0.03,*SNAP* will measureM to  0.01 andw0 to  0.05.

## Dark Energy Equation of State

- Is w = -1?  By measuring the evolution of w to high precision (few %), SNAP will determine the nature of the Dark Energy.
- For a flat universewith prior Mmeasuredto  0.03,SNAP will measurew0  to  0.05 andw  to  0.27.

## SNAP works and plays well with others     w0 and w

## Conclusions

- Dark energy is the dominant fundamental constituent of our Universe, yet we know very little about it.
- SNAP will test theories of dark energy and show how the expansion rate has varied over the history of the Universe.
- A vigorous R&D program, supported by the DoE is underway, leading to an expected launch early in the next decade.
- NASA and DoE have agreed to partner on a Joint Dark Energy Mission (JDEM).  SNAP is a prime candidate for JDEM.

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