“Observing Dark Energy” Bob Nichol ICG, Portsmouth Special thanks to Masao Sako, David Weinberg, Andy Connolly, Albert Stebbins, Rob Crittenden, Daniel.

Download “Observing Dark Energy” Bob Nichol ICG, Portsmouth Special thanks to Masao Sako, David Weinberg, Andy Connolly, Albert Stebbins, Rob Crittenden, Daniel.

Post on 28-Dec-2015

214 views

Category:

Documents

2 download

Embed Size (px)

TRANSCRIPT

  • Observing Dark EnergyBob NicholICG, PortsmouthSpecial thanks to Masao Sako, David Weinberg, Andy Connolly, Albert Stebbins, Rob Crittenden, Daniel Eisenstein, Josh Frieman, Tom Giannantonio, Ryan Scranton, Will PercivalSDSS, DES & WFMOS teams

    Durham "Cosmic Frontiers"

  • OutlineDark Energy PrimerGrowth of Structure: ISWGeometry: SN & BAO

    Durham "Cosmic Frontiers"

  • (DARK) MATTER(DARK) ENERGYCMBSNSNe and CMB force us into a Universe ~75% DE and ~25% DM. We are trace elements! Can this be true?

    Durham "Cosmic Frontiers"

  • Understanding Dark EnergyWe can make progress on questions:Is DE just a cosmological constant (w(z)=-1)? (Make better observations and push to higher z) Is DE a new form of matter (with negative effective pressure) or a breakdown of GR? (Study DE using different probes)

    But there are only two broad avenues:Geometrical tests (SN, BAO) Growth of structure (CL, WL) No compelling theory, so must be observational driven

    Durham "Cosmic Frontiers"

  • DETF Report (Kolb et al)

    138 pages condensed to this columnSN & BAO - safe, but only 100% improvement

    CL & WL - risky, but big gainsClear recommendation to do multiple measurement with one being the growth of structure to test GR

    Durham "Cosmic Frontiers"

  • The effect of DE is only seen on large scales, therefore we need to study large volumes to beat cosmic varianceDE is a small effect (even on large scales) so need large samples to control statistical and systematic errorsWe need to understand the redshift evolution of DE (w(z))DE require big surveysChallenge to experimentalists to build massive surveys (in size and number) with high precision

    Durham "Cosmic Frontiers"

  • Massive SurveysSDSS: first massive survey ISW SDSSII SNeBaryon Acoustic Oscillations (BAO)DES: next massive imaging surveyThe power of photo-zs

    WFMOS: next massive redshift surveyThe power of spectroscopy

    Durham "Cosmic Frontiers"

  • SDSSwww.sdss.orgDR5: Million spectra, 8000 sq degsExtension (2005-2008): Legacy, SNe, Galaxy

    Durham "Cosmic Frontiers"

  • Stage I & II: Growth of Structure

    Durham "Cosmic Frontiers"

  • Late-time Integrated Sachs Wolfe (ISW) EffectDE also effects the growth of structure i.e. Poisson equation with dark energy:

    In a flat, matter-dominated universe (CMB tells us this), then density fluctuations grow as:

    Therefore, for a flat geometry, changes in the gravitational potential are a direct physical measurement of Dark Energy as they should be non-evolving if DE=0

    Durham "Cosmic Frontiers"

  • Durham "Cosmic Frontiers"

  • Experimental Set-upNolta et al, Boughn & Crittenden, Myers et al, Ashfordi et al, Fosalba et al., Gaztanaga et al., Rassat et al.

    Durham "Cosmic Frontiers"

  • WMAP-SDSS cross-correlationWMAP W bandLuminous Red Galaxies (LRGs)No signal in a flat, matter dominated Universe

    Durham "Cosmic Frontiers"

  • ISW Detected5300 sq degrees Achromatic (no contamination)Upto 5 detectionUpdate of Scranton et al. 2003

    Durham "Cosmic Frontiers"

  • Theoretical PredictionsW-band z=0.49 LRGsm=0.3m=0.2Degeneracy between b, n(z) and cosmology

    Durham "Cosmic Frontiers"

  • Giannantonio et al. 2006(astro-ph/0607572)WMAP3-photoQSOWMAP3 best fitDetection of DE at z>10.075
  • Evolution of DEw=-1 survives another (weak) test

    But rules out models with D(z=1.5) > 0.5

    Important for tests of modified gravity theories

    Durham "Cosmic Frontiers"

  • Stage I & II: Geometrical Tests

    Durham "Cosmic Frontiers"

  • SDSSII SNe SurveyExploring DE & SNe at an epoch when DE dominates

    bridge low-z (z

  • Use the SDSS 2.5m telescopeSeptember 1 - November 30 of 2005-2007Scan 300 square degrees of the sky every 2 daysStripe82 (UKIDSS data)Survey AreaNS

    Durham "Cosmic Frontiers"

  • Durham "Cosmic Frontiers"

  • Photometric TypingColor-type SNe candidates using nightly g r i datafit light-curve for redshift, extinction, stretch for Ia

    Able to type with >90% efficiency after ~2 - 4 epochsIaIaIISN2005hyII

    Durham "Cosmic Frontiers"

  • International Follow-up332 spectroscopically confirmed SN Ia254 unconfirmed Ias with good LCs (galaxy redshifts exist for 60)Many Ias now have multi-epoch spectraFollow-up on NTT, WHT, Subaru, ARC3.5m, HET, MDMOne more season, expecting over 500 SNe

    Durham "Cosmic Frontiers"

  • 2005 spectroscopically confirmed + probable SN Ia

    Durham "Cosmic Frontiers"

  • dispersion ~ 0.18 maginternal consistency

    Durham "Cosmic Frontiers"

  • Galaxy-SNe Correlations

    Durham "Cosmic Frontiers"

  • Baryon Oscillation Gravity squeezes the gas, pressure pushes back! They oscillate When the Universe cools below 3000K these sound waves are frozen in Courtesy of Wayne Hu

  • Cosmic Microwave Background Effect of this sound wave already discovered in relic light of the early universe i.e. the CMB! That was the Universe at 400,000 years. Can we see these sound waves today?

  • BAO 2006(Percival et al. 2006)WMAP3SDSS DR5 520k galaxiesm=0.24 bestfit WMAP modelMiller et al. 2001, Percival et al. 2001, Tegmark et al. 2001, Cole et al. 2005, Eisenstein et al. 2005, Hutsei 2006, Blake et al. 2006, Padmanabhan et al. 2006

    Durham "Cosmic Frontiers"

  • Smooth + sinc function(Blake & Glazebrook 2003)

    Durham "Cosmic Frontiers"

  • One parameter Standard ruler(flat,h=0.73,b=0.17)Percival et al. 2006Best fit m=0.2699.74% detection (3)

    Durham "Cosmic Frontiers"

  • m - h Degeneracyh=0.720.08 HSTm=0.256+0.049-0.029m0.275h WMAP3m=0.256+0.029-0.024mh2 WMAP3m=0.256+0.019-0.023

    Durham "Cosmic Frontiers"

  • SummaryISW detected at several redshifts to z~1 and consistent with cosmological constant. Good news for people looking for DE at high z229 SDSS SNIas so far, 400 by 2007 Systematics limited and will deliver w to 6% BAO have been detected at 3 m=0.256 to 10% from acoustic scaleGood news for future BAO experiments

    Durham "Cosmic Frontiers"

  • Future Experiments(Stage III)

    Durham "Cosmic Frontiers"

  • Dark Energy Survey (DES)5000 sq deg multiband (g,r,i,z) survey of SGP using CTIO Blanco with a new wide-field camera40 sq deg time domain search for SNe

    Cluster counts from optical+SPTWeak lensing mapsSNe Ia distance measurement study from 2000 SneUnable to gain spectroscopic follow-up for all these Sne. Must use photometric classifications and redshiftsUse SDSSII as a training sample to prepare for DESGalaxy angular power spectrum for 300 million galaxies Baryon Acoustic Oscillations from photo-zs

    Each will independently constrain the dark energy eqn of state

  • The Dark Energy Survey UK Consortium (I) PPARC funding: O. Lahav (PI), P. Doel, M. Barlow, S. Bridle, S. Viti, J. Weller (UCL), R. Nichol (Portsmouth), G. Efstathiou, R. McMahon, W. Sutherland (Cambridge), J. Peacock (Edinburgh) Submitted a proposal to PPARC in February 2005 requesting 1.5 M for the DES optical design. In March 2006, PPARC Council announced that it will seek participation in DES.

    (II) SRIF3 funding: R. Nichol, R. Crittenden, R. Maartens, W. Percival (ICG Portsmouth) K. Romer, A. Liddle (Sussex)Funding the optical glass blanks for the UCL DES optical work

    These scientists will work together through the UK DES Consortium and are collaborating with the Spanish DES Consortium

    Durham "Cosmic Frontiers"

  • DES Photo-zsDES science relies on good photometric estimates of the 300 million expected galaxies ANNz: Collister & Lahav 2005, Abdalla et al.Simulated DESSimulated DES+VISTAgrizgrizJK

    Durham "Cosmic Frontiers"

  • DES + VISTA + VSTGive photo-zs to z~2 with < 0.1BAO improves by 50% with VISTA; 15% error on w just the BAO scaleTargets for Gemini, VLTOverlap with CLOVER, SPT DES + Planck ISW will be better than LSST for non-constant w models(Pogosian et al. 2005)

    Durham "Cosmic Frontiers"

  • WFMOSProposed MOS on Subaru via an international collaboration of Gemini and Japanese astronomers1.5deg FOV with 4500 fibres feeding 10 low-res spectrographs and 1 high-res spectrographFirst-light in 2013~20000 spectra a night (2dfGRS at z~1 in 10 nights)DE science, Galactic archeology, galaxy formation studies and lots of ancillary science from database

    Durham "Cosmic Frontiers"

  • Distance Scalez~1 survey with 2 million galaxies with twice LRG volume1% accuracyKAOS purple book (Seo, Eisenstein, Blake, Glazebrook)WFMOS will measure w to
  • Testing Modified GravityDGPLCDM 7 differenceYamamoto et al. 2006

    Durham "Cosmic Frontiers"

  • Summary IIExperiments by 2010 will measure w (constant) to a few %, but that doesnt mean we understand it!Next generation surveys will probe w(z) and start testing growth of structure measurements of DE

    Durham "Cosmic Frontiers"

Recommended

View more >