Constraining Dark Energy with the Large Synoptic Survey Telescope Hu Zhan UC Davis

Outline Dark energy probes The Large Synoptic Survey Telescope Supernovae, cluster counting, baryon acoustic oscillations (BAO), weak lensing (WL), cosmic microwave background (CMB), gamma-ray bursts, SMBBH in-spirals… The Large Synoptic Survey Telescope Dark energy, dark matter, Solar system, optical transients (SN, GRB, NEO), galactic map LSST BAO and WL Photo-zs, systematic noises, joint analysis of BAO and WL Summary 6/21/2006 LANL

Evidence for Dark Energy Spergel et al. (2006) 6/21/2006 LANL

Dark Energy Probes Probe Measurements Remarks Supernovae DL(z) Presently most powerful Clusters DA(z), H(z), & G(z) Large systematic errors, need to understand nonlinear astrophysics (e.g., mass—observable relation, mass function, both mean & scatter, …) BAO DA(z) & H(z) Emerging, less affected by astrophysical uncertainties, less powerful WL DA(z) & G(z) Emerging, potentially powerful, limited by systematic errors CMB DLSS & Late ISW Relatively weak constraints Dark Energy Task Force report 6/21/2006 LANL

Supernova Distances Low-z SNe are needed. SN constraints on dark energy equation of state parameters are sensitive to the mean curvature. Subject to evolutional uncertainties 6/21/2006 LANL

Cluster Counting LCDM: Wm=0.27 (dotted line), Wm=0.3 (solid line), Wm=0.33 (shot-dashed line) OCDM: long-dashed lines Wm=0.27, 0.3, 0.33 (top to bottom) Haiman, Mohr, & Holder (2001) 6/21/2006 LANL

Large Synoptic Survey Telescope The 8.4-meter primary 10 deg2 FOV 3 billion pixels 0.3 - 1 µm (ugrizy) 15-s exposures 15 TB/night 200 PB total Key Missions: Dark energy Solar system Optical transients Galactic map 20,000 deg2 survey area r = 26.5 mag ~109 galaxies ~106 SNe ~104 clusters First light ~ 2012 www.lsst.org National Optical Astronomy Observatory Research Corporation The University of Arizona University of Washington Brookhaven National Laboratory Harvard-Smithsonian Center for Astrophysics Johns Hopkins University Las Cumbres Observatory, Inc. Lawrence Livermore National Laboratory Stanford Linear Accelerator Center Stanford University The Pennsylvania State University University of California, Davis University of Illinois at Urbana-Champaign

LSST Supernovae z = 0.8 z = 0 SN spectrum has many features that are useful for determining its redshift photometrically. The maximum error in the mean redshift is 0.01 near z = 0.7. Typical errors are 5 to 10 times smaller. This is better than galaxy photo-zs. Pinto, Smith, & Garnavich (205th AAS) Wang, Pinto, & Zhan (207th AAS) 6/21/2006 LANL

LSST Clusters Shear-selected clusters: false detections, completeness, uncertainties of the mass function… 6/21/2006 Wang et al. (2004)

(Angular & radial scales) BAO as a Standard Ruler + RS~150 Mpc Angular diameter distance & Hubble parameter (Sound horizon at recombination) RS = c Dz/H = Dq D (Angular & radial scales) 6/21/2006 LANL

Cosmic Shear The cosmic shear is a tiny gravitational distortion to the shapes of galaxies. The shear power spectrum measures the potential fluctuations of the intervening cosmic field. The lensing kernel is geometric. Wittman et al. (2000) 6/21/2006 LANL

Formalism potential PS (BAO) (WL) I choose to normalize the galaxy/shear power spectrum to the dimensionless potential power spectrum, because potential perturbations are more fundamental than density perturbations. WL shear and CMB temperature fluctuations are driven directly by the fluctuations in the gravitational potential. 6/21/2006 LANL

Angular Power Spectra Galaxy PS Shear PS Song & Knox (2004) Zhan (astro-ph/0605696) 6/21/2006 LANL

Photo-z u band helps reduce the confusion between the Lyman break and Balmer break LSST photo-z calibration plan 6/21/2006 LANL

Number of Bins wa w0 4000 sq deg WL alone Photo-z error distribution uncertain w0 Ma, Hu, & Huterer (2006) Zhan, astro-ph/0605696 6/21/2006 LANL

Photo-z Degradation to WL Constraints Huterer et al. (2006) 6/21/2006 LANL

Photo-z Degradation to WL Constraints Degradation without bound! Ma, Hu, & Huterer (2006) 6/21/2006 LANL

Angular Galaxy Power Spectra Sensitivity to photo-z bias 6/21/2006 LANL

Tomographic Binning Gaussian P(zph | z), sz = sz0(1 + z) Ma, Hu, & Huterer (2006) Gaussian P(zph | z), sz = sz0(1 + z) n(z) can be quite complex. 6/21/2006 LANL

Systematics LSST BAO LSST WL sz = 0.05(1+z), 50 galaxies/arcmin-2, EP = s(wp)×s(wa), Nsys – additive systematic noise 6/21/2006 LANL

Multiplicative Systematics Huterer et al. (2006) 6/21/2006 LANL

Additive Systematics Huterer et al. (2006) 6/21/2006 LANL

Complementarity Galaxy clustering bias Photo-z bias Photo-z rms Spectroscopic calibrations must be carried out to map the photo-z error distribution! 6/21/2006 LANL

Constraints on Galaxy Bias and Photo-zs Schneider et al., astro-ph/0606098 6/21/2006 LANL

Constraints on Galaxy Bias and Photo-zs Schneider et al., astro-ph/0606098 6/21/2006 LANL

LSST BO + WL sP(sz) = sz/20 , Nsys = 10-8 6/21/2006 LANL

Curvature? BO & WL not affected by WK no systematic noise 1000 sq deg spectroscopic survey: w0—wa degrades quite a bit if no high-z data; even worse if WK is unknown. BO & WL not affected by WK Knox, Song, & Zhan (astro-ph/0605536) 6/21/2006 LANL

Dark Energy Models w0 & wa effects on qs cancel each other. SUGRA? w0 & wa effects on qs cancel each other. Same qs, wm, wb, … 6/21/2006 LANL

Summary BAO and WL are highly complementary to each other. One should use multiple techniques jointly to constrain dark energy, whenever possible. Photo-z calibration with spectroscopy is crucial to achieve BAO self-calibration of the photo-z error distribution. Systematic errors must be well controlled especially for the WL technique. The impact of non-Gaussian photo-z error distribution on dark energy constraints needs to be quantified. There are many other challenges. For instance, we do not know the nonlinear matter power spectrum to 1% even without baryons. 6/21/2006 LANL