Cosmology Surveys (a non-WHT talk) - Dark Energy science and beyond - Imaging surveys - Spectroscopic surveys Ofer Lahav University College London

“Evidence” for Dark Energy Observational data • Type Ia Supernovae • Galaxy Clusters • Cosmic Microwave Background • Large Scale Structure • Gravitational Lensing • Integrated Sachs-Wolfe Physical effects: • Geometry • Growth of Structure Both depend on the Hubble expansion rate: H 2 (z) = H 2 0 [  M (1+z) 3 +  DE (1+z) 3 (1+w) ] (flat)

Dark Energy Pre-SNIa

• Peebles (1984) advocated Lambda • APM result for low matter density (Efstathiou et al. 1990) • Baryonic fraction in clusters (White et al. 1993) • The case for adding Lambda (Ostriker & Steinhardt 1995) • Others… Calder & OL, Physics World, Jan 2010

What will be the next paradigm shift?

• Vacuum energy (cosmological constant)?

• Dynamical scalar field?

– w=p/  – for cosmological constant: w = -1 • Manifestation of modified gravity?

• Inhomogeneous Universe? • What if cosmological constant after all?

• Multiverse - Landscape?

• The Anthropic Principle?

Standard rulers

Baryonic Acoustic Oscillations

Comving distance SDSS Luminous Red Galaxies Density fluctuations z=0.5

Harmonic l CMB WMAP Temperature fluctuations z=1000

Probing the Geometry of the Universe with Supernovae Ia ‘Union’ SN Ia sample (Kowalski et al. 2008)

In 3 Dimensions

Massey et al. 2007

Galaxy Surveys 2010-2020

Photometric surveys : DES, Pan-STARRS, HSC, Skymapper, PAU, LSST, Euclid (EIC), JDEM(SNAP like), … Spetroscopic surveys : WiggleZ, BOSS, BigBOSS, hetdex, WFMOS/Sumire, Euclid (NIS) JDEM (Adept like), SKA, …

Photometric redshifts

• Probe strong spectral features (e.g. 4000 break) • Template vs. Training methods

z=0.1

z=3.7

MegaZ-LRG

Photoz scatter of 0.04

• Input: 10,000 galaxies with spectra • Train a neural network •ANNz, Collister & Lahav 2004 • Output: 1,000,000 photo-z •Collister, Lahav et al. 2007 •Update using 6 photo-z methods *Abdalla et al. 2009 3 (Gpc/h) 3 : the largest ever galaxy redshift survey!

Neutrino mass from MegaZ-LRG

Total mass < 0.3 eV (95% CL) Thomas, Abdalla & OL (2009) 0911.5291

The Dark Energy http://www.darkenergysurvey.org

The DES Collaboration

an international collaboration of ~100 scientists from ~20 institutions US: Fermilab, UIUC/NCSA, University of Chicago, LBNL, NOAO, University of Michigan, University of Pennsylvania, Argonne National Laboratory, Ohio State University, Santa-Cruz/SLAC Consortium UK Consortium: UCL, Cambridge, Edinburgh, Portsmouth, Sussex, Nottingham Spain Consortium: CIEMAT, IEEC, IFAE Brazil Consortium: Observatorio Nacional, CBPF,Universidade Federal do Rio de Janeiro, Universidade Federal do Rio Grande do Sul CTIO

The Dark Energy Survey (DES)

• Proposal: – Perform a 5000 sq. deg. survey of the southern galactic cap – Measure dark energy with 4 complementary techniques • New Instrument: – Replace the PF cage with a new 2.2 FOV, 520 Mega pixel optical CCD camera + corrector • Time scale: – Instrument Construction 2008-2011 • Survey: – 525 nights during Oct.– Feb. 2011-2016 – Area overlap with SPT SZ survey and VISTA VHS Use the Blanco 4m Telescope at the Cerro Tololo Inter-American Observatory (CTIO)

C2

The 5 lenses are now being polished

C1 Polishing & coating coordinated by UCL (with 1.7M STFC funding)

Euclid Imaging Surveys

Wide Survey : Extragalactic sky (20,000 deg 2 = 2 p sr) • Visible: Galaxy shape measurements to

RIZ

AB ≤ 24.5 (AB, 10σ) at 0.16” FWHM, yielding 30-40 resolved galaxies/amin 2 , with a median redshift

z

~ 0.9

• NIR photometry: Y, J, H ≤ 24 (AB, 5σ PS), yielding photo-z’s errors of 0.03-0.05(1+

z

) with ground based complement (PanStarrs-2, DES. etc) • Concurrent with spectroscopic survey • • Deep Survey : 40 deg 2 at ecliptic poles Monitoring of PSF drift (40 repeats at different orientations over life of mission) Produces +2 magnitude in depth for both visible and NIR imaging data.

Possible additional Galactic surveys: • • Short exposure Galactic plane High cadence microlensing extra-solar planet surveys could be easily added within Euclid mission architecture.

Wide Extragalactic 20,000 deg 2 Galactic Plane Deep ~40 deg 2

SDSS Spectroscopic Surveys 2MRS CfA 2dFGRS

SUBARU: the ups and downs of WFMOS and the hopes for SUMIRE

Redshift Distortion as a test of Modified Gravity Guzzo et al. 2008

BigBOSS:

The Ground-Based Stage IV BAO Experiment

A new 5000-fiber R=5000 spectrograph covering a 3 degree diameter field will measure BAO and redshift space distortions in the distribution of galaxies and hydrogen gas spanning redshifts from 0.2 < z < 3.5. The Dark Energy Task Force figure of merit (DETF FoM) for this experiment is expected to be equal to that of a JDEM mission for BAO with the lower risk and cost typical of a ground-based experiment • http://bigboss.lbl.gov/

Cosmology Surveys summary

* Goal: Dark Energy parameters to a few % level • Both imaging and spectroscopy surveys are essential • Is a BAO survey with a 4m feasible?

• Non-DE science with DE surveys (e.g. Neutrino mass, galaxy evolution, MW structure, QSOs)

THE END

Planned photometric and spectroscopic surveys

The Dark Energy problem: 10, 90 or 320 years old?

The weak field limit of GR: F = -GM/r 2 +  /3 r X * “I have now explained the TWO principle cases of attraction… which is very remarkable” Isaac Newton, Principia (1687) Lucy Calder & OL A&G Feb 08 issue http://www.star.ucl.ac.uk/~lahav/CLrev.pdf

(revised)

Dark Energy Science Program

Four Probes of Dark Energy • Galaxy Clusters • clusters to z>1 • • SZ measurements from SPT Sensitive to growth of structure and geometry • Weak Lensing • Shape measurements of 300 million galaxies • Sensitive to growth of structure and geometry • Large-scale Structure • 300 million galaxies to z = 1 and beyond • Sensitive to geometry • Supernovae • 15 sq deg time-domain survey • • ~3000 well-sampled SNe Ia to z ~1 Sensitive to geometry Plus QSOs, Strong Lensing, Milky Way, Galaxy Evolution

DES Forecasts: Power of Multiple Techniques

w

(

z

)

=w 0 +w a

(1

–a

) 68% CL FoM factor 4.6

tigther compared to near term projects

The Chequered History of the Cosmological Constant  * The old CC problem: Theory exceeds observational limits on  by 10 120 !

* The new CC problem: Why are the amounts of Dark Matter and Dark Energy so similar?

Photo-z –Dark Energy cross talk

• Approximately, for a photo-z slice: (  w/ w) = 5 (  z/ z) = 5 (  z /z) N s -1/2 => the target accuracy in w and photo-z scatter  z dictate the number of required spectroscopic redshifts N s =10 5 -10 6

Euclid - impact on Cosmology

Current+WMAP Planck Weak Lensing Imaging Probes Euclid Euclid +Planck Factor Gain

Δw p

0.13

0.03

0.018

0.016

0.01

13

ΔW a

0.17

0.15

0.13

0.066

>15

ΔΩ m

0.01

0.008

0.006

0.004

0.003

0.0008

13

ΔΩ Λ

0.015

0.04

0.02

0.012

0.003

5

ΔΩ b

0.0015

0.0007

0.012

0.007

0.005

0.0004

4

Δσ 8

0.026

0.05

0.013

0.0009

0.003

0.0015

17

Δn s

0.013

0.005

0.02

0.014

0.006

0.003

4

Δh

0.013

0.007

0.1

0.07

0.020

0.002

7

DE FoM

~10 180 400 500 1500 150 Euclid Imaging will challenge all sectors of the cosmological model: • Dark Energy:

w p

and

w a

with an error of 2% and 13% respectively (no prior) • Dark Matter: test of CDM paradigm, precision of 0.04eV on sum of neutrino masses (with Planck) • Initial Conditions: constrain shape of primordial power spectrum, primordial non-gaussianity • Gravity: test GR by reaching a precision of 2% on the growth exponent  (

d

ln  m /

d

ln

a

 m  )  Uncover new physics and Map LSS at 0