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## Observational windows of cosmological physics

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**Observational windows of cosmological physics**张鹏杰（Zhang, Pengjie) 中国科学院上海天文台 Shanghai Astronomical Observatory Chinese Academy of Science Connecting fundamental physics with observations, KITPC, 2009**The dark universe**The visible world • The dark universe • Dark matter? • Dark energy? • Modified gravity? • Violation of EP, Lorentz invariance? • Violation of Corpernican • Principle? Connecting fundamental physics with observations, KITPC, 2009**Windows to the dark universe**21cm Soon to detect Connecting fundamental physics with observations, KITPC, 2009**General relativity and GR tests**• perihelion shift • light deflection • time dilation/frequency shift • orbital decay (gravitational wave) • time delay • geodetic effect • ?frame dragging effect (e.g. General covariance Tensor analysis Field equation Equivalence principle • Confirmed at 10^(-13) General principle of relativity Connecting fundamental physics with observations, KITPC, 2009**GR and cosmology: dark matter**If only baryons and photons exist, density fluctuations today <10^-2. Even worse at smaller scales Density fluctuations in baryons are ~10^-5 at ~100 Mpc/h at z~1100 Density fluctuations today are ~0.1 at 100 Mpc/h X So dark matter must exist, whose rms fluctuation must be orders of magnitude larger than that in baryons at CMB epoch! Connecting fundamental physics with observations, KITPC, 2009**GR and modern cosmology: non-zero cosmological constant**Riess et al. 2005 • Cosmic acceleration • DL-z relation from cosmic standard candles SNe Ia, 1998- • Decay of gravitational potential (the Integrated Sachs-Wolfe effect) 2003- Connecting fundamental physics with observations, KITPC, 2009**The story of the Vulcan planet**Newtonian gravity predicts the Mercury orbit to be closed (if Sun+Mercury only) Observations found that the Mercury orbit is not closed and theperihelion procession is 43 arcsec/century Theory conflicts with observation→New mass?Flaw in Newtonian gravity? Le Verrier (the one predicted Neptune) postulated the planet Vulcan We now know Vulcan does not exist and instead, Newtonian gravity goes wrong Connecting fundamental physics with observations, KITPC, 2009**Connecting fundamental physics with observations, KITPC,**2009**To describe the universe**• Zero order (The overall expansion and geometry) • First order (The large scale structure) example: H in flat CDM and DGP Modified gravity for dark energy Connecting fundamental physics with observations, KITPC, 2009**Probes of the expansion**• Type Ia supernovae (standard candles) • Baryon acoustic oscillation in LSS and CMB (standard ruler) • Fundamental plane, Faber-Jackson & Tully-Fisher of galaxies • Age (globular clusters, galaxy age-z..) • Gravitational lensing time delay • SZ-X ray cluster fluxes • Cluster gas fraction • Gamma ray bursts • Alcock-Paczynski (AP) test • ..... Connecting fundamental physics with observations, KITPC, 2009**Expansion rate to test gravity**DPG is disfavored comparing to LCDM reminder: H in flat CDM and DGP Stage IV: SNAP, LSST, etc. thousands well calibrated SNe Ia sub-1% accuracy in DL Song et al. 2006 Connecting fundamental physics with observations, KITPC, 2009**Baryon acoustic oscillations as cosmological standard rulers**tell us the distance and H(z) tell us the distance Eisenstein, et al. 2005 astro-ph/0501171 Connecting fundamental physics with observations, KITPC, 2009**BAO:clean physicsmeasures both D(z) and H(z)Stage IV**projects: SKA, ADEPT, HSHS,etc. Can reach sub-1% accuracy Blake et al. 2006 Connecting fundamental physics with observations, KITPC, 2009**Some near and far future probes**• Near future • Water maser orbital motion measurement • Far future • Gravitational wave of black hole binaries • Sandage-Loeb test (temporal shift in Lyman-alpha absorption lines) Connecting fundamental physics with observations, KITPC, 2009**Water maser: a semi-absolute distance indicator**water maser Observing these water maser cloud for years to measure the proper motion and acceleration Barvainis & Antonucci, astro-ph/0506245 Connecting fundamental physics with observations, KITPC, 2009**Water maser: a semi-absolute distance indicator**Connecting fundamental physics with observations, KITPC, 2009 astro-ph/9907013**Sandage-Loeb test**Lyman-alpha absorption (Lyman-alpha forest) • Observe the lines for decades and measure motion against time • A measure on H A. Sandage, Astrophys. J. 139, 319 (1962). A. Loeb, Astrophys. J. 499, L111 (1998), [astro- ph/9802122]. observables Connecting fundamental physics with observations, KITPC, 2009**Unique tool to measure H(z) at z~3**Corasaniti et al., arXiv:astro-ph/0701433v1 Connecting fundamental physics with observations, KITPC, 2009**Standard Sirens: gravitational waves fromSMBBH and short**GRB(e.g. Hughes & Holz, 2003; Dalal et al. 2006) • Gravitational wave of binaries can be used for self-calibrated precision distance measurement (Challenge: position?) • Short GRB: can be well localized • Low z GRB will fix H0 • High z SMBBH: measure w GRB 050509b The first short GRB been located SMBBH detected by Chandra Connecting fundamental physics with observations, KITPC, 2009**SMBBH**Hughes and Holz astro-ph/0212218 Solar mass BBH Dalal et al. astro-ph/0601275 Connecting fundamental physics with observations, KITPC, 2009**expansion**probes GRB: D cluster: fgas, SZ/X-ray: D weak lensing: D SL: H GW: D GW SMBBH: D maser: D 21cm BAO: D, H BAO: D,H SN: D CMB: D 0 1 6 50 1100 2 redshift Connecting fundamental physics with observations, KITPC, 2009**Probes of the large scale structure**They may not probe what we think that they probe!! • gravitational potentials • Gravitational lensing • Galaxy/cluster peculiar velocities • The integrated Sachs-Wolfe effect • density • galaxy clustering • cluster abundance • fluid velocity • The kinetic Sunyaev Zel'dovich effect? ? Refer to Jain & ZPJ, 2008, PRD for details ? Connecting fundamental physics with observations, KITPC, 2009**Gravitational lensing**Anisotropies and non-Gaussianity in cosmic backgrounds (CMB, 21cm, etc.) Preliminary detection in WMAP Distortion in galaxy shape（cosmic shear) Sophisticated method Change in galaxy number density （cosmic magnification) Detected Connecting fundamental physics with observations, KITPC, 2009**How to do precision lensing measurement**• Cosmic shear (by far the most sophiscated) • Even with galaxy disk orientation measurement! (Morales, 2007 arXiv:astro-ph/0608494) • Lensing of cosmic backgrounds • CMB lensing • Seljak & Zaldarriaga, Zaldarriaga & Seljak 1998;Hu & Oakamoto 2002 • 21 cm background lensing • Cooray 2004; Pen 2004; Zahn & Zaldarriaga 2006; Mandel & Zaldarriaga 2006; But non-Gaussianity! • Lensing magnification in flux • Ia supernovae • Cooray et al. 2006; Dodelson & Vallinotto 2006; but see ZPJ & Corasaniti 2007 • Galaxy fundamental plane • Bertin & Lombard 2006; but see ZPJ & Corasaniti 2007 • Cosmic magnification (lensing induced galaxy density fluctuations) • Magnification-galaxy (Scrantan et al. 2005) • Magnification-magnification • ZPJ & Pen 2005, 2006 (find ways to eliminate galaxy clustering and thus enables the lensing-lensing measurement) Connecting fundamental physics with observations, KITPC, 2009**CMB vs. Lensing**Connecting fundamental physics with observations, KITPC, 2009**Lensing tomography**COSMOS-3D lensing－》3D distribution of dark matter Connecting fundamental physics with observations, KITPC, 2009**Weak lensing and cosmological applications**Refregier 2003 Schneider 2005 Munshi et al. 2006 Hoekstra & Jain 2008 Nonlinear structure growth rate. Probes DM, DE, gravity and neutrino mass, Lensing kernel: tells us the distance-redshift relation and the curvature of the universe Linear power spectrum: probes primordial fluctuations and tests inflation lensing power spectrum: observable Connecting fundamental physics with observations, KITPC, 2009**Great progress!**Cosmic shear has been measured robustly! CFHTLS:i band, 57deg2 Fu et al. 2007 also, Hoekstra et al. 2005 Eventually, 5 bands, 170 deg2 B mode: Measure of systematics Connecting fundamental physics with observations, KITPC, 2009**Stage IV: LSST, SKA, Euclid, etc.**• ~20000 deg^2 • billions galaxies • sub-1% in power spectrum Connecting fundamental physics with observations, KITPC, 2009**The dark energy task force recommends four**• probes of the expansion: SN and BAO • probes of structure growth: weak lensing and cluster abundance Peculiar velocity as the fifth!! Part 2 Figure of merit for stage IV space projects Connecting fundamental physics with observations, KITPC, 2009**Distinguishing DE/MG: (1) Global fit**LCDM DGP is less favored, or even ruled out DGP H. Zhang et al. 2008 Fang et al. 2008 Connecting fundamental physics with observations, KITPC, 2009**Weak lensing/LSS and Yukawa-like gravity**Dore et al. 2007 arXiv:0712.1599 Connecting fundamental physics with observations, KITPC, 2009**For future data,**Zhao et al. 2008 Connecting fundamental physics with observations, KITPC, 2009**Distinguishing DE/MG: (2) Smoking guns**D(GW) • Independent methods to measure the distances. • D(EM): from EM waves (SN, BAO, maser, etc) • D(GW): from gravitational waves (GW) • If gravity is GR in 4D, then D(GW)=D(EM) • Otherwise, interesting things can happen • Example: if GW can leak into the 5th dimension, • D(GW)>D(EM) D(EM) Deffayet & Menou, 2007 Connecting fundamental physics with observations, KITPC, 2009**To test gravity, we need to break the dark degeneracy I: MG**and DE can mimic each other exactly in H(z) produced by any model There are always dark energy models with degenerate H! To distinguish between DE and MG, one must have LSS, besides the overall expansion of the universe! Connecting fundamental physics with observations, KITPC, 2009**Consistency check of GR at cosmological scales**The rate of structure growth The expansion rate Consistency relation observables Connecting fundamental physics with observations, KITPC, 2009**Consistency check of GR: Real data!!**Expansion Consistent with GR structure growth Wang et al. 2007 arXiv:0705.0165 Connecting fundamental physics with observations, KITPC, 2009**Sign for MG?**Sign for nothing? Wait a second Expansion structure growth Wang et al. 2007 arXiv:0705.0165 Connecting fundamental physics with observations, KITPC, 2009**Future surveys can do much better**Underlying gravity: 5D braneworld DGP Fit with GR Ishak et al. 2005 Also Knox et al. 2005 Connecting fundamental physics with observations, KITPC, 2009**We need multiple probes of LSS to break the**dark degeneracy II: modifications in gravity and DE/DM may mimic each other in some LSS It is possible for a dark energy model to reproduce gravitational lensing and matter density fluctuations in DGP(Kunz & Sapone 2006) • Two extra degrees of freedom in dark energy models • the anisotropic stress • pressure fluctuations • Two extra degrees of freedom in modified gravity models • Newton's constant • relation between two potentials Kunz & Sapone 2006 See also Bashinsky 2007 Hu & Sawichi 2007 Connecting fundamental physics with observations, KITPC, 2009**Linear level large scale structure (LSS) in LCDM，general**dark energy models and modified gravity models. 4 perturbation variables: δ,v: perturbations in fluidΦ,ψ: perturbations in space-time Ma & Bertschinger 1995 Hu & Eisenstein 1999 ZPJ et al. 2007 Amendola et al. 2007 Holds for LCDM, DGP, f(R), Yukawa, etc. Extra perturbations in MOND scalar and vector fields Connecting fundamental physics with observations, KITPC, 2009**Break the dark degeneracy II**One necessary condition for DE to mimic MG If 3 or more independent LSS variables can be measured, modified gravity models can be unambiguously discriminated from DE/DM Jain & ZPJ, 2008 Connecting fundamental physics with observations, KITPC, 2009**In the afternoon, I will talk about**• Large scale peculiar velocity as a probe of gravity • Testing the Copernican principle Connecting fundamental physics with observations, KITPC, 2009**Part 2Peculiar velocity: a window to the dark universe**• Matter distribution in our universe is inhomogeneous • Gravitational attraction arising from inhomogeneity perturbs galaxies and causes deviation from the Hubble flow v=Hr v=Hr v v peculiar velocity r r Connecting fundamental physics with observations, KITPC, 2009**http://www.astr.ua.edu/keel/galaxies/distance.html**Connecting fundamental physics with observations, KITPC, 2009**What makes peculiar velocity special and important to probe**gravity? • At scales larger than galaxy clusters, only respond to gravity • In linear regime, honest tracer of matter distribution • Necessary for the complete phase-space description of the universe Connecting fundamental physics with observations, KITPC, 2009**Early applications of peculiar velocity: (1) A brave new**world with gigantic structures Shapely concentration • GREAT attractor(s), with far more mass than expected, must exist in order to pull the Milky way at ～600 km/s with respect to CMB • Such gigantic structures should be no coincidence, if we believe in the cosmological principle Great attractor Connecting fundamental physics with observations, KITPC, 2009**Early applications of peculiar velocity: (2) road to the**standard LCDM cosmology • Largely based on peculiar velocity measurements of local and nearby galaxies, some cosmologists (e.g. Jim Peebles) argued that the the cosmological constant may exist and account for ~80% of the energy budget of the universe, in early 80s. Connecting fundamental physics with observations, KITPC, 2009**How to measure peculiar velocity?Traditional method**Measure the recession velocity from the redshift v=Hr v Subtract the Hubble flow to obtain the peculiar velocity r Measure the distance through FP,TF,FJ,SN, etc. Connecting fundamental physics with observations, KITPC, 2009**A factor of 3 larger than the LCDM prediction**Not so right asymptotic behaviour Watkins et al. 2008 Connecting fundamental physics with observations, KITPC, 2009

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