Yun Wang, 09/28/2006

Dark Energy SearchDark Energy Search

Yun Wang Yun Wang

September 28, 2006September 28, 2006

Yun Wang, 09/28/2006

beware of the dark side …

Master Yoda

Yun Wang, 09/28/2006

OutlineOutline

• Most promising methods for dark energy search

• What do current data tell us about dark energy?

• What are the future prospects for probing dark energy?

Yun Wang, 09/28/2006

What is dark energy?What is dark energy?

Two Possibilities:

(1) Unknown energy component(1) Unknown energy component

(2) Modification of Einstein’s theory of general (2) Modification of Einstein’s theory of general relativity (a.k.a. Modified Gravity)relativity (a.k.a. Modified Gravity)

Yun Wang, 09/28/2006

How We Probe Dark Energy:How We Probe Dark Energy:

• Cosmic expansion history H(z)Cosmic expansion history H(z)

tells us whether DE is a cosmological constanttells us whether DE is a cosmological constant• Growth history of cosmic large scale structure G(z)Growth history of cosmic large scale structure G(z)

tells us whether general relativity is modifiedtells us whether general relativity is modified

Yun Wang, 09/28/2006

Three Most Promising Three Most Promising Methods for Dark Energy Methods for Dark Energy

SearchSearch• SNe Ia (Standard Candles):SNe Ia (Standard Candles):

method through which DE has been discovered; independent of clustering of matter, probes H(z)

• Weak Lensing Tomography and Cross-Weak Lensing Tomography and Cross-Correlation Cosmography: Correlation Cosmography:

probes clustering of matter G(z), and H(z)

• Baryon Acoustic Oscillations (Standard Ruler): Baryon Acoustic Oscillations (Standard Ruler): calibrated by CMB, probes H(z)

Yun Wang, 09/28/2006

Type Ia Supernovae as Type Ia Supernovae as Standard CandlesStandard Candles

Yun Wang, 09/28/2006

Calibration of SNe IaCalibration of SNe Ia Phillips 1993 Riess, Press, & Kirshner 1995 L. Wang et al. 2003

Brighter SNe IaBrighter SNe Iadecline more slowlydecline more slowly make a correction make a correction to the brightness based to the brightness based on the decline rate.on the decline rate.

26 SNe Ia with Bmax-Vmax 0.20 fromthe Calan/Tololo sample[Hamuy et al. 1996, AJ, 112, 2398]

Yun Wang, 09/28/2006

SNe Ia as Cosmological Standard SNe Ia as Cosmological Standard CandlesCandles

Systematic effects: dust: can be constrained using multi-color data.

(Riess et al. 1998; Perlmutter et al. 1999)

gray dust: constrained by the cosmic far infrared background. (Aguirre & Haiman 2000)

gravitational lensing: its effects can be reduced by flux-averaging. (Wang 2000; Wang, Holz, & Munshi

2002)

SN Ia evolution (progenitor population drift):Once we obtain a large number of SNe Ia at high z

(z > 1), we can disregard SN Ia events that have no counterparts at high z, and only compare like with like. (Branch et al., astro-ph/0109070)

Yun Wang, 09/28/2006

Weak Lensing of SNe Weak Lensing of SNe IaIa

Kantowski, Vaughan, & Branch 1995 Frieman 1997 Wambsganss et al. 1997 Holz & Wald 1998 Metcalf & Silk 1999 Wang 1999

WL of SNe Ia can be modeled by a Universal Probability Distribution for Weak Lensing Magnification (Wang, Holz, & Munshi 2002)

The WL systematic of SNe Ia can be removed by flux averaging (Wang 2000; Wang & Mukherjee 2003)

Yun Wang, 09/28/2006

Ultra Deep Supernova SurveyUltra Deep Supernova Survey

To determine whether SNe Ia are good cosmological standard candles, we need to nail the systematicuncertainties (luminosity evolutionluminosity evolution, gravitational gravitational lensinglensing, dustdust). This will require at least hundreds of SNe Ia at z>1z>1. This can be easily accomplished by doing an ultra deep supernova survey using a dedicated dedicated telescopetelescope, which can be used for other thingssimultaneously (weak lensing, gamma ray burstafterglows, etc).

Wang 2000a, ApJ (astro-ph/9806185)

Yun Wang, 09/28/2006

Go Deep!Go Deep!Wang & Lovelave 2001, ApJ Lett 562, 115

Optimal for measurement of dark energy density:

Yun Wang, 09/28/2006

Weak Lensing Tomography Weak Lensing Tomography and Cross-Correlation and Cross-Correlation

CosmographyCosmography

Yun Wang, 09/28/2006

• Weak Lensing Tomography:Weak Lensing Tomography: compare observed cosmic shear correlations with theoretical/numerical predictions to measure G(z) [Wittman et al. 2000]

• WL Cross-Correlation WL Cross-Correlation CosmographyCosmography measure the relative shear signals of galaxies at different distances for the same foreground mass distribution: gives distance ratios that can be used to obtain H(z) [Jain & Taylor 2003]

Yun Wang, 09/28/2006

Baryon Baryon acoustic acoustic

oscillations as oscillations as a standard a standard

rulerruler

Blake & Glazebrook 2003

Seo & Eisenstein 2003

Yun Wang, 09/28/2006

Detection of BAO in the SDSS dataDetection of BAO in the SDSS data [Eisenstein et al. 2005]

Yun Wang, 09/28/2006

Wang 2006

Yun Wang, 09/28/2006

Wang 2006

Yun Wang, 09/28/2006

Wang 2006

Yun Wang, 09/28/2006

What do current data What do current data tell us about dark tell us about dark

energy?energy?

Yun Wang, 09/28/2006

Constraints on 2-parameter model tightenedConstraints on 2-parameter model tightened

Wang & Tegmark (2004) Wang & Mukherjee (2006)

Yun Wang, 09/28/2006

Model-independent constraints remain weakModel-independent constraints remain weak

Left: Wang & Tegmark (2004)

Right: Wang & Mukherjee (2006)

Yun Wang, 09/28/2006

Deceleration parameter q0=m/2-

Evidence for Evidence for cosmic acceleration cosmic acceleration is strengthened.is strengthened.

Wang & Tegmark (2005)Wang & Mukherjee (2006)

Yun Wang, 09/28/2006

What are the future What are the future prospects for probing prospects for probing

dark energy?dark energy?

Yun Wang, 09/28/2006

Future Dark Energy Survey Future Dark Energy Survey (an incomplete list)(an incomplete list)

• Essence (2002-2007): 200 SNe Ia, 0.2 < z < 0.7, 3 bands, t ~ 2d • Supernova Legacy Survey (2003-2008): 2000 SNe Ia to z=1• ESO VISTA (2005?-?): few hundred SNe, z < 0.5 • CFHT Legacy (2003-2008): 2000 SNe Ia, 100’s high z SNe, 3 bands, t ~

15d• Pan-STARRS (2006-?): all sky WL, 100’s SNe y, z < 0.3, 6 bands, t = 10d

• HETDEX (?): 200 sq deg BAO, 1.8 < z < 3.• WFMOS on Subaru (?): 2000 sq deg BAO, 0.5<z<1.3 and 2.5<z<3.5• ALPACA (?): 50,000 SNe Ia per yr to z=0.8, t = 1d , 800 sq deg WL &

BAO with photo-z’s• Dark Energy Survey (?): cluster at 0.1<z<1.3, 5000 sq deg WL, 2000 SNe at

0.3<z<0.8

• LSST (2013-): 106 SNe Ia y, z < 0.8, 6 bands, t = 4d; 20,000 sq deg WL & BAO with photo-z’s.

• JDEM (2015?): several competing mission concepts

Yun Wang, 09/28/2006

How many methods How many methods should we use to probe should we use to probe

DE?DE?• The challenge to solving the DE mystery

will not be the statistics of the data obtained, but the tight control of systematic effects inherent in the data.

• A combination of the three most promising methods (each optimized by having its systematics minimized by design) provides the tightest control of systematics.

Yun Wang, 09/28/2006

Joint Efficient Dark-energy Joint Efficient Dark-energy Investigation (JEDI):Investigation (JEDI):

a candidate implementation of JDEM http://jedi.nhn.ou.edu/

Yun Wang, 09/28/2006

JEDI CollaborationJEDI CollaborationPI: Yun Wang (U. of Oklahoma)Deputy PI: Edward Cheng (Conceptual Analytics)

Scientific Steering Committee:Arlin Crotts (Columbia), Tom Roellig (NASA Ames), Ned Wright (UCLA)

SN Lead: Peter Garnavich (Notre Dame), Mark Phillips (Carnegie Observatory)WL Lead: Ian Dell’Antonio (Brown)BAO Lead: Leonidas Moustakas (JPL)

Eddie Baron (U. of Oklahoma) David Branch (U. of Oklahoma)Stefano Casertano (Space Telescope Insti.) Bill Forrest (U. of Rochester)Salman Habib (LANL) Mario Hamuy (U. of Chile)Katrin Heitmann (LANL) Alexander Kutyrev (NASA GSFC)John MacKenty (Space Telescope Insti.) Craig McMurtry (U. of Rochester)Judy Pipher (U. of Rochester) William Priedhorsky (LANL)Robert Silverberg (NASA GSFC) Volker Springel (Max Planck Insti.)Gordon Squires (Caltech) Jason Surace (Caltech)Max Tegmark (MIT) Craig Wheeler (UT Austin)

Yun Wang, 09/28/2006

JEDI: the Power of Three JEDI: the Power of Three Independent MethodsIndependent Methods

Supernovae as standard candles: luminosity distances dL(zi)

Baryon acoustic oscillations as a standard ruler:

cosmic expansion rate H(zi) angular diameter distance dA(zi)

Weak lensing tomography andcosmography:

cosmic structure growth historyG(z); ratios of dA(zi)/dA(zj)

The three independent methods will provide a powerful cross check,and allow JEDI to place precise constraints on dark energy.

Yun Wang, 09/28/2006

ConclusionConclusion

Dark energy search methods’ checklist: 1) Supernovae as standard candles; 2) Weak lensing tomography and cosmography; 3) Baryon acoustic oscillations as standard ruler.

Current data (SNe Ia, CMB, and LSS) are consistent with a constant X(z) at 68% confidence. However, the reconstructed X(z) still has large uncertainties at z > 0.5.

A successful JDEM can place definitive constraints on the time dependence of X(z). This will have a fundamental impact on particle physics and cosmology.